Answer:
x =72
Step-by-step explanation:
The sum of the angles of a triangle is 180 degrees
x+77+31 = 180
Combine like terms
x + 108 = 180
Subtract 108 from each side
x+108-108 = 180-108
72⁰
By angle sum property:
x + 77 + 31 = 180
x = 180 - 108
x = 72⁰
