Step-by-step explanation:
Scince 3 and 4 are forming a straight angle together which we knew it's equal to 180°
m<3 + m<4 = 180°
m<3 = 180°- m<4
m<3= 180°- 81=99°
The sum of triangle angle = 180
m<1 + m<2 + m<3 =180°
42° + m<2 + 99° = 180°
m<2 = 180° - 99° - 42°
m<2= 39°
