Question 551073
Let x = original angle


(180 - x) = 10(90 - x)


180 - x = 900 - 10x


180 - 900 = -10x + x


-720 = -9x


-720/-9 = x


80 = x


The Prove:


Let x = 80


180 - x = 10(90 - x)


180 - 80 = 10(90 - 80)


100 = 10(10)


100 = 100


The original angle is 80 degrees.