What is the value of x?

A

Step-by-step explanation:

5x and 128 are adjacent angles and sum to 180° , then

5x + 128 = 180 ( subtract 128 from both sides )

5x = 52 ( divide both sides by 5 )

x = 10.4 → A

These angles are what we call supplementary angles, which means that the sum of each angle should amount to the measure of a straight angle, 180°

So, we can form an equation.

128+5x=180

Solve using the normal steps.

128-128+5x=180-128

5x=52

x=10.4

Therefore, x=10.4

If you want to check, substitute x in 5x for 10.4.

5(10.4)=52

So, the angles each measure 52° and 128°.

Add them to see if they are 180° together.

52+128=180°

Therefore, x=10.4