Answer:
∠ 7 = 80°
Explanation:
∠ 1 and ∠ 2 are a linear pair and sum to 180° , that is
∠ 1 + ∠ 2 = 180
x + 20 + x = 180
2x + 20 = 180 ( subtract 20 from both sides )
2x = 160 ( divide both sides by 2 )
x = 80
then
∠ 2 = x = 80°
∠ 2 and ∠ 7 are alternate angles and are congruent , so
∠ 7 = 80°