m∠DEG = 109
m∠GEF = 71
m∠DEG + m∠GEF = ∠DEF
Then you would substitute ∠DEG for 109 and ∠GEF for 71.
109 + 71 = m∠DEF
180 = m∠DEF
To solve this faster, I know that DEF is a supplementary angle and supplementary angles equal 180 degrees. So, m∠DEF would equal 180.
Hope this helps :))
