Resposta:

a) y + y = 180, logo y = 90

b) 2x + x = 90, logo x = 30

c) 4x + x = 180, logo x = 36

d) 130 + y + y = 180, logo 130 + 2y = 180; 2y = 180 - 130; 2y = 50; y = 50: 2; y = 25.