Answer:
y=20
Explanation:
since angles on a straight line =180°
and we are given half of the line(90°)
so we know we are left with another 90°
the angle opposite 30=30 because. opposite angles r equal
so then we now have the equation
180=(90+30)+3y
180=120+3y
180-120=3y
60=3y
dividing by 3
y=20