Angle 3 = 10x becuase they are vertically opposed angles.
10x = 4x + 42 because they are corresponding angles resulting from a line that crosses paralell lines.
Then. you can solve for x:
10x - 4x = 42
6x = 42
x = 42 / 6
x = 7
Measure of the angle 3 = 10x = 10(7) = 70.
Answer: 70.
