How do I answer this question?

Due to the Triangle Angle Sum Theorem, we know that the sum of the interior angles of a triangle equals 180 degrees, therefore,

180 = m<1 + m<2 + m<3

180 - m<3 = m<1 + m<2

But, we also know that m<4 + m<3 = 180 degrees.

180 = m<3 + m<4

180 - m<3 = m<4

Both m<4 and m<1 + m<2  equals 180 - m<3

m<4 = m<1 + m<2