Question 1177469
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m&ang;1 + m&ang;2 + m&ang;3 = 180&deg;         Sum of angles of a triangle is 180&deg;

m&ang;4 + m&ang;3 = 180&deg;               Supplementary angles add to 180&deg;

m&ang;1 + m&ang;2 - m&ang;4 = 0           Subtracted bottom eqn from top eqn

m&ang;1 + m&ang;2 = m&ang;4               Added m&ang;4 to both sides, (DONE)