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# 2.6: Equations with Decimals, Fractions and Parentheses

Difficulty Level: At Grade Created by: CK-12

Pens are $9 per dozen and pencils are$6 per dozen. Janet need to buy a half dozen of each for school. How much is the total cost of her purchase?

### Guidance

Recall that the distributive property is a mathematical way of grouping terms. It states that the product of a number and a sum is equal to the sum of the individual products of the number and the addends. Here, you will use the distributive property with linear equations and fractions. The same rules apply. You have to multiply what is on the outside of the parentheses by what is on the inside of the parentheses and this is your first step in solving equations with one variable where there are parentheses. After you remove parentheses, you then solve the equation by combining like terms, moving constants to one side of the equals sign, variables to the other side of the equals sign, and finally isolating the variable to find the solution.

#### Example A

Solve: \begin{align*}\frac{2}{5}(d+4) = 6\end{align*}.

Find the LCD for 5, 5, and 1. Since it is 5, multiply the last number by \begin{align*}\frac{5}{5}\end{align*}, to get the same denominator.

Since all of the denominators are the same, the equation becomes:

Therefore \begin{align*}d = 11\end{align*}.

#### Example B

Solve: \begin{align*}\frac{1}{4}(3x+7) =2\end{align*}.

Find the LCD for 4, 4, and 1. Since it is 4, multiply the last number by \begin{align*}\frac{4}{4}\end{align*}, to get the same denominator.

Since all of the denominators are the same, the equation becomes:

Therefore \begin{align*}x = -5\end{align*}.

#### Example C

Solve: \begin{align*}\frac{1}{3}(x-2) = -\frac{2}{3}(2x+4)\end{align*}.

Since all of the denominators are the same, the equation becomes:

Therefore \begin{align*}x=\frac{-6}{5}\end{align*}.

#### Concept Problem Revisited

Pens are $9 per dozen and pencils are$6 per dozen. Janet need to buy a half dozen of each for school. How much is the total cost of her purchase?

First you should write down what you know:

Let \begin{align*}x =\end{align*} total cost

Cost of pens: $9/dozen Cost of pencils:$6/dozen

Janet needs one half dozen of each.

The total cost would therefore be:

Therefore Janet would need \$7.50 to buy these supplies.

### Vocabulary

Distributive Property
The distributive property is a mathematical way of grouping terms. It states that the product of a number and a sum is equal to the sum of the individual products of the number and the addends. For example, in the expression: \begin{align*}{\color{red}\frac{2}{3}} ({\color{blue}x + 5})\end{align*}, the distributive property states that the product of a number \begin{align*}({\color{red}\frac{2}{3}})\end{align*} and a sum \begin{align*}({\color{blue}x + 5})\end{align*} is equal to the sum of the individual products of the number \begin{align*}({\color{red}\frac{2}{3}})\end{align*} and the addends \begin{align*}({\color{blue}x}\end{align*} and \begin{align*}{\color{blue}5})\end{align*}.

### Guided Practice

1. Solve for x: \begin{align*}\frac{1}{2}(5x+3)=1\end{align*}.

2. Solve for x: \begin{align*}\frac{2}{3}(9x-6)=2\end{align*}.

3. Solve for x: \begin{align*}\frac{2}{3}(3x+9)=\frac{1}{4}(2x+5)\end{align*}.

1.

Find the LCD for 2, 2, and 1. Since it is 2, multiply the last number by \begin{align*}\frac{2}{2}\end{align*}, to get the same denominator.

Since all of the denominators are the same, the equation becomes:

Therefore \begin{align*}x=\frac{-1}{5}\end{align*}.

2.

Find the LCD for 3, 3, and 1. Since it is 3, multiply the last number by \begin{align*}\frac{3}{3}\end{align*}, to get the same denominator.

Since all of the denominators are the same, the equation becomes:

Therefore \begin{align*}x=1\end{align*}.

3.

Find the LCD for 3, 3, and 4, 4. Since it is 12, multiply the first two fractions by \begin{align*}\frac{4}{4}\end{align*} and the second two fractions by \begin{align*}\frac{3}{3}\end{align*}, to get the same denominator.

Since all of the denominators are the same, the equation becomes:

Therefore \begin{align*}x=\frac{-57}{18}\end{align*}.

### Practice

Solve for the variable in each of the following problems.

1. \begin{align*}\frac{1}{2} (x+5)=6\end{align*}
2. \begin{align*}\frac{1}{4}(g+2)=8\end{align*}
3. \begin{align*}0.4(b+2)=2\end{align*}
4. \begin{align*}0.5(r-12)=4\end{align*}
5. \begin{align*}\frac{1}{4}(x-16)=7\end{align*}

Solve for the variable in each of the following problems.

1. \begin{align*}26.5-k=0.5(50-k)\end{align*}
2. \begin{align*}2(1.5c+4)=-1\end{align*}
3. \begin{align*}-\frac{1}{2}(3x-5)=7\end{align*}
4. \begin{align*}0.35+0.10(m-1)=5.45\end{align*}
5. \begin{align*}\frac{1}{4}+\frac{2}{3}(t+1)=\frac{1}{2}\end{align*}

Solve for the variable in each of the following problems.

1. \begin{align*}\frac{1}{2}x-3 (x+4)=\frac{2}{3}\end{align*}
2. \begin{align*}-\frac{5}{8}x+x=\frac{1}{8}\end{align*}
3. \begin{align*}0.4(12-d)=18\end{align*}
4. \begin{align*}0.25(x+3)=0.4(x-5)\end{align*}
5. \begin{align*}\frac{2}{3}(t-2)=\frac{3}{4}(t+2)\end{align*}

## Date Created:

Dec 19, 2012

Nov 04, 2015
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