Question

Which equation can be used to find the value of x?

109=180
x+42=67
x=180-109
42+67-x=180

Answer 1

C

Explanation:

We know every triangle equals 180 so were just going to take 180 - 42 = 138 then were going to do 138 - 67 = 71 we can check our work by doing

42 + 67+ 71 = 180. We also know 67 + 42 = 109.

Lets look at our answers;

A. 109 = 180 + x When solved it gave me; x = -71. We got a positive 71 so this is incorrect.

B. x + 42 = 67 When solved it gave me; x = 25, which is incorrect.

C. x = 180 - 109 When solved it gave me; x = 71

D. 42 + 67 - x = 180 When solved it gave me; x = - 71

Therefore the answer is C.