11) ∠Q+∠R+∠S=180°
let ∠Q=∠S=x
x+58+x=180
2x=122
x=61
since∠Q=∠S=x
∴∠Q=∠S=61°
12) M+N+P=180
x+2x-1+2x+1=180
5x=180
x=36
∴m=36
n=2x-1
=72-1
=71
p=2x+1
=72+1
=73
13) her answer is not reasonable because they are angles on a straight line and sum of angles on a straight line =180 and 86+86≠ 180.
Hope this was helpful.
