1.5: Algebra Expressions with Fraction Bars
What if you had a mathematical expression containing fraction bars, like
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CK12 Foundation: 0105S Evaluate Algebraic Expressions with Fraction Bars
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For more practice, you can play an algebra game involving order of operations online at http://www.funbrain.com/algebra/index.html.
Guidance
Fraction bars count as grouping symbols for PEMDAS, so we evaluate them in the first step of solving an expression. All numerators and all denominators can be treated as if they have invisible parentheses around them. When real parentheses are also present, remember that the innermost grouping symbols come first. If, for example, parentheses appear on a numerator, they would take precedence over the fraction bar. If the parentheses appear outside of the fraction, then the fraction bar takes precedence.
Example A
Use the order of operations to evaluate the following expression:
Solution:
We substitute the value for
Although this expression has no parentheses, the fraction bar is also a grouping symbol—it has the same effect as a set of parentheses. We can write in the “invisible parentheses” for clarity:
Using PEMDAS, we first evaluate the numerator:
We can convert
Then evaluate the expression:
Example B
Use the order of operations to evaluate the following expression:
Solution:
We substitute the values for
This expression has nested parentheses (remember the effect of the fraction bar). The innermost grouping symbol is provided by the fraction bar. We evaluate the numerator
Example C
Evaluate the expression
Solution
Store the values of
Press [ENTER] to obtain the answer
Watch this video for help with the Examples above.
CK12 Foundation: Evaluate Expressions with Fraction Bars
Vocabulary
 Fraction bars count as grouping symbols for PEMDAS, so we evaluate them in the first step of solving an expression. All numerators and all denominators can be treated as if they have invisible parentheses around them.
Guided Practice
Use the order of operations to evaluate the following expression:
Solution:
We substitute the values for
This complicated expression has several layers of nested parentheses. One method for ensuring that we start with the innermost parentheses is to use more than one type of parentheses. Working from the outside, we can leave the outermost brackets as parentheses
Practice
For 13, use the order of operations to evaluate the following expressions.

2⋅(3+(2−1))4−(6+2)−(3−5) 
4+7(3)9−4+12−3⋅22 
(22+5)252−42÷(2+1)
For 45, evaluate the following expressions involving variables.

jkj+k whenj=6 andk=12 
x+y2y−x whenx=2 andy=3
For 69, evaluate the following expressions involving variables.

4x9x2−3x+1 whenx=2 
z2x+y+x2x−y whenx=1, y=−2, andz=4 
4xyzy2−x2 whenx=3, y=2, andz=5 
x2−z2xz−2x(z−x) whenx=−1 andz=3
For 1014, evaluate each expression using a graphing calculator.

x2+2x−xy whenx=250 andy=−120 
(xy−y4)2 whenx=0.02 andy=−0.025 
x+y−zxy+yz+xz whenx=12, y=32, andz=−1 
(x+y)24x2−y2 whenx=3 andy=−5 
(x−y)3x3−y+(x+y)2x+y4 whenx=4 andy=−2
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Fraction Bar
A fraction bar is a line used to divide the numerator and the denominator of a fraction. The fraction bar means division.Order of Operations
The order of operations specifies the order in which to perform each of multiple operations in an expression or equation. The order of operations is: P  parentheses, E  exponents, M/D  multiplication and division in order from left to right, A/S  addition and subtraction in order from left to right.Parentheses
Parentheses "(" and ")" are used in algebraic expressions as grouping symbols.PEMDAS
PEMDAS (Please Excuse My Daring Aunt Sally) is a mnemonic device used to help remember the order of operations: Parentheses, Exponents, Multiplication/Division, Addition/Subtraction.Image Attributions
Here you'll learn how to apply the order of operations to evaluate algebraic expressions containing fraction bars for specific variable values.