Answer:
m<A = 50°
Explanation:
supplementary angles add up to 180°
m<B = 2x + 30
we don't know m<A, so we'll say the value of it is x
2x + 30 + x = 180°
3x + 30 = 180
3x = 150
x = 50
plug this value back in for x
m<B = 2(50) + 30 = 130
m<B = 130°
m<A = x = 50
m<A = 50°
to prove these are supplementary angles, 130 + 50 = 180