plissss bantuin kakak kakak

a° + b° = 180°
a = 180 - b atau b = 180 - a

a.
a = 1/2 b
a = 1/2 (180 - a)
a = 90 - 1/2a
a + 1/2a = 90
3/2a = 90
a = 90/(3/2) = 180/3 = 60°

b.
b = 3a
b = 3 (180 - b)
b = 540 - 3b
b + 3b = 540
4b = 540
b = 540/4 = 135°

c.
a = 2b - 20
a = 2 (180 - a) - 20
a = 360 - 2a - 20
a + 2a = 360 - 20
3a = 340
a = 340/3 = 133,33°

d.
2b = 4a + 40
2b = 4 (180 - b) + 40
2b = 720 - 4b + 40
2b + 4b = 720 + 40
6b = 760
b = 760/6 = 126,7°