Answer:
Step-by-step explanation:
The interior angles of a heptagon add up to 5*180 = 900
So
x + 143 + 116 + 135 + 135 + 116 + 155 = 900 Add up the known angles
x + 800 = 900 Subtract 800 from both sides
x + 800 - 800 = 900 - 800 Combine
x = 100
