Ta có: 3 x A = 2 x B => A = 2/3 x B
5 x B = 3 x C => C = 5/3 x B
Lại có: A + B + C = 180
=> 2/3 x B + B + 5/3 x B = 180
=> B x ( 2/3 + 5/3 + 1) = 180
=> B x 10/3 = 180
=> B = 180 : 10/3 = 54
=> A = 54 x 2/3 = 36
=> C = 54 x 5/3 = 90
Đáp số: A = 36
B = 54
C = 90