Question

an exterior angle of a triangle measure 120° and its interior opposite angles are in the ratio 5:7. find the angles of the triangle

Answer 1

let the angle be 5x and 7x
5x+7x = 120
12x= 120
x= 10
1st angle = 50
2nd = 70
3rd= 180-120
= 60

Answer 2

firstly we find interior angle by lpp(linear pair property )
so
let angle a =1
now
angle1 + 120=180
angle 1 =60
now

by angle sum property we find other two angles
let 2nd angle be 5x
and 3rd angle be 7x
now,
7x + 5x + 60° = 180°
12x = 180° - 60°
12x=120°
x=120/12

x=10

now
angle 1 =60°
angle 2 =5x =5 ×10=50°
angle 3=7x=7×10=70°

hope it helps you