To find the value of x, the angles must equal the same number at the end (corresponding angles)
4x = 3x + 10
isolate the x to find the value of x
4x (-3x) = 3x (-3x) + 10
4x - 3x = 10
x = 10
Check:
4(10) = 40
3(10) + 10 = 30 + 10 = 40 (True)
10 is your answer for x
hope this helps