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Exercises Numbers, fractions and percents

Example 4.101 from Prealgebra, 4.7 Solve Equations with Fractions

Solve Equations with Fractions: example 4.101

Solve: $- y = 15 .$

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
One way to solve the equation is to rewrite $- y$ as $−1 y,$ and then use the Division Property of Equality to isolate $y .$

Rewrite $- y$ as $−1 y$ .

Divide both sides by −1.

Simplify each side.

Another way to solve this equation is to multiply both sides of the equation by $−1 .$

Multiply both sides by −1.

Simplify each side.

The third way to solve the equation is to read $- y$ as “the opposite of $y .”$ What number has $15$ as its opposite? The opposite of $15$ is $−15 .$ So $y = −15 .$

For all three methods, we isolated $y$ is isolated and solved the equation.

Check:

Substitute $y = −15$ .

Simplify. The equation is true.

Your turn

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

Solve: $- y = 48 .$

How did it go?

PreviousSolve Equations with Fractions: example 4.100 Next Solve Equations with Fractions: example 4.102

From Prealgebra (1st edition) by OpenStax (Rice University), section 4.7, 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.