angles sum: 180(6-2) = 720
50 + 37 + 42 = 129
129 + 5x + 7x - 1 + 3x + 40 = 720
15x + 168 = 720
15x = 552
x = 36.8
check:
129 + 5(36.8) + (3(36.8) + 40) + (7(36.8) - 1) = 720
Correct answer??
180-50 = 130
180-37 = 143
180-42 = 138
Known internal angles:
130 + 143 + 138 = 411
15x + 39 + 411 = 720
15x = 270
x = 18
