first, find out x x+15+2x+15=180 3x+30=180 3x=150 x=50 so the two angels are x+15=65(let's name is ∠5 for convenience), and ∠6= 2x+15=115 notice the two inner lines are marked as congruent, so ∠4=∠5=65 ∠1=180-∠4-∠5=180-65-65=50 Name the right bottom angle ∠7, ∠3=∠7 and ∠3+∠7=the exterior angle 100 degree, therefore, ∠3=50 ∠2+∠3=∠4, therefore, ∠2=∠4-∠3=65-50=15 ∠1=50, ∠2=15, ∠3=50, ∠4=65
