I don't know why you included a Z as there is no Z point in the image, but I'll assume it was a mistake.
Answer:
134
Explanation:
Angles on a straight line are supplementary (add up to 180), therefore we can know that the sum of both angles are 180.
3x + 5 + x + 3 = 180
Combine like terms.
4x + 8 = 180
Subtract 8 from 180 (If you move a number onto the other side of the equal sign it becomes opposite. ex: 3 becomes -3)
4x = 172
172 divided by 4.
x = 43
Plug in x into the equations.
3(43) + 5
129 + 5
PQR = 134
