Question 497984
A = x - 5
B = x 
C = x + 12
x - 5 + x + x + 12 = 180
3x + 7 = 180
3x = 173.
B = 57.7 degrees
A = 52.7 degrees
C = 69.7 degrees
57.7 + 52.7 + 69.7 = 180.1 degrees, approx 180 degrees with a round off error.
Cleomenius.