Besar sudut B adalah

<C = 180°-110° = 70°

<A + <B + <C = 180
3x + 3x - 10 + 70 = 180
6x + 60 = 180
6x = 180 - 60
6x = 120
x = 20

<A = 3x = 3 × 20 = 60°
<B = 3x - 10 = 3 × 20 - 10 = 60 -10 = 50°

Jadi sudut B 50°