in this problem we have that
y+20=x+15 -------> by vertical angles
isolate variable y
y=x+15-20
y=x-5 ------> equation A
and
(3x+5)+(x+15)=180 ------> by form a linear pair (sipplementary angles)
solve for x
4x+20=180
4x=160
x=40
substitute the value of x in equation A
y=40-5
y=35
therefore
x=40 and y=35