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Exercises Expressions, exponents and radicals

Example 7.8 from Prealgebra, 7.2 Commutative and Associative Properties

Commutative and Associative Properties: example 7.8

Evaluate each expression when $x = \frac{7}{8} .$

ⓐ $x + 0.37 + (- x)$
ⓑ $x + (- x) + 0.37$

Work it out on paper first. Then open the solution one step at a time, and stop as soon as you can finish on your own.

Solution

ⓐ

Substitute $\frac{7}{8}$ for $x$ .

Convert fractions to decimals.

Add left to right.

Subtract.

ⓑ

Substitute $\frac{7}{8}$ for x.

Add opposites first.

What was the difference between part ⓐ and part ⓑ? Only the order changed. By the Commutative Property of Addition, $x + 0.37 + (- x) = x + (- x) + 0.37 .$ But wasn’t part ⓑ much easier?

Your turn

The book's Try It right after this example: same idea, new numbers. Only the answer is given.

Evaluate each expression when $y = \frac{3}{8} :$ ⓐ $y + 0.84 + (- y)$ ⓑ $y + (- y) + 0.84 .$

How did it go?

PreviousCommutative and Associative Properties: example 7.7 Next Commutative and Associative Properties: example 7.9

From Prealgebra (1st edition) by OpenStax (Rice University), section 7.2, licensed under CC BY 4.0. Original at openstax.org. We split the solution into steps; the words, numbers and figures are the book's. OpenStax doesn't endorse this site.