I'm assuming you're comparing two triangles? If not, then this is probably wrong. Triangle = 180 degrees 180 divided by 3 = 60 degrees since ∠1 ≅ ∠2 ≅ ∠3, each angle equal 60 degrees ∠4 ≅ ∠5 m∠4 = m∠3 + 10 m∠3 + 10 = m∠5 we know that m∠3 is 60 degrees. 60 + 10 = 70, so m∠5 is 70 degrees 70 degrees is the answer.