We are asked to find the value of x in the following image:
Where we see that the addition of the angle that measures 39 degrees plus the angle indicated as 3x degrees, must give us a right angle (that is 90 degrees) in order to be the suplementary angle to a right angle formed at the intersection Z
So we can write the following equation:
39 + 3 x = 90
and solve for x by subtracting 39 from both sides
3 x = 90 - 39
3 x = 51
divide both sides by 3 in order to isolate x completely
x = 51 / 3
x = 17
