How do I get the answer to this step by step?

Step-by-step explanation:

The exterior angle is 151 degrees. The theorem states that the sum of its 2 remote interior angles, 5x+3 and 9x-20, will add up to this exterior angle. Therefore,

5x+3+9x-20 = 151 and

14x - 17 = 151 and

14x = 151 + 17

14x = 168 so

x = 12

If you want to find out the measure of each of these angles, just plug in 12 for x and do the math:

5(12) + 3 = 63 and

9(12) - 20 = 88 and

88 + 63 = 151 as it should.