Question

How do I solve for
2w + 9 = 8w + 21

Answer 1

w = -2

Explanation:

The properties of equality allow us to manipulate an equation to solve for a certain variable.

Solving for w

To help us solve we can use the subtraction property of equality, which says that an equation stays equal if the same value is subtracted from both sides.

First, rewrite the equation.

• 2w + 9 = 8w + 21

Next, subtract 2w from both sides.

• 9 = 6w + 21

Then, subtract 21 from both sides.

• -12 = 6w

Finally, divide both sides by 6.

• -2 = w

Checking the Answer

To check our answer we can plug it back into the equation.

• 2(-2) + 9 = 8(-2) + 21

Then evaluate as you would any equation.

• 5 = 5

This means that -2 must be correct.