Notice that "x" and "3x+20" are supplementary angles so their sum is 180°
(x) + (3x + 20) = 180
4x + 20 = 180
4x = 160
x = 40
To solve for "y", you have 2 options: either notice that "x" and "y-20" are supplementary angles so their sum is 180° or notice that "3x + 20" and "y - 20" are vertical angles so are equal to each other. I am going to solve using the first option because it is less work.
(x) + (y - 20) = 180°
40 + y - 20 = 180
y + 20 = 180
y = 160
Answer: x=40, y=160