# 7.1: Solve for the Unknown

**At Grade**Created by: CK-12

Can you use the order of operations? What's the value of ? In this concept, we will learn to use the order of operations.

### Guidance

The **order of operations** tells us the correct order of evaluating math expressions. We always do ** parenthesis first**. Then we do

**and finally**

*multiplication and division (from left to right)***.**

*addition and subtraction (from left to right)*In order to evaluate expressions using the order of operations, we can use the problem solving steps to help.

- First,
**describe**what you see in the problem. What operations are there? - Second, identify what
**your job**is. In these problems, your job will be to solve for the unknown. - Third, make a
**plan**. In these problems, your plan should be to use the order of operations. - Fourth,
**solve**. - Fifth,
**check**.

#### Example A

Figure out the value of the variable. Follow the order of operations.

**Solution:**

We can use the problem solving steps to help.

**Describe:** The equation has parenthesis, multiplication, addition and subtraction.

**My Job:** Do the operations to figure out the value of .

**Plan:** Do the parenthesis first. Then do the multiplication. Finally, do the subtraction and addition from left to right.

**Solve:** First do the parenthesis:

- Next do the multiplication:
- Last do the subtraction and addition:

**Check:**

#### Example B

Figure out the value of the variable. Follow the order of operations.

**Solution:**

We can use the problem solving steps to help.

**Describe:** The equation has parenthesis, division, addition and subtraction.

**My Job:** Do the operations to figure out the value of .

**Plan:** Do the parenthesis first. Then do the division. Finally, do the subtraction and addition from left to right.

**Solve:** First do the parenthesis:

- Next do the division:
- Last do the subtraction:

**Check:**

#### Example C

Figure out the value of the variable. Follow the order of operations.

**Solution:**

We can use the problem solving steps to help.

**Describe:** The equation has multiplication, division and addition.

**My Job:** Do the operations to figure out the value of .

**Plan:** Do the multiplication and division first from left to right. Then do the addition.

**Solve:** First do the multiplication and division:

- Last do the addition:

**Check:**

#### Concept Problem Revisited

We can use the problem solving steps to help.

**Describe:** The equation has parenthesis, division, multiplication and addition.

**My Job:** Do the operations to figure out the value of .

**Plan:** Do the parenthesis first. Then, do the multiplication and division from left to right. Finally do the addition.

**Solve:** First do the parenthesis:

- Next do the multiplication and division from left to right:
- Last do the addition:

**Check:**

### Vocabulary

** Order of operations** tell us the correct order of evaluating math expressions. We always do

**. Then we do**

*Parenthesis first***and finally**

*multiplication and division (from left to right)***.**

*addition and subtraction (from left to right)*### Guided Practice

Figure out the value of the variables. Follow the order of operations.

1.

2.

3.

**Answers:**

1.

2.

3.

### Practice

Figure out the value of the variables. Follow the order of operations.

### Image Attributions

Students follow the order of operations to solve for the value of unknowns. Students use problem solving steps to help.