Answer:
∠ 1 = 120°
Explanation:
5x + 15 and 3x - 3 are same- side interior angles and sum to 180° , then
5x + 15 + 3x - 3 = 180 , that is
8x + 12 = 180 ( subtract 12 from both sides )
8x = 168 ( divide both sides by 8 )
x = 21
Then
5x + 15 = 5(21) + 15 = 105 + 15 = 120
∠ 1 and 5x + 15 are corresponding angles and are congruent , so
∠ 1 = 120°