writing a multi step equation for a real world situation

Question

the sum of the angle measures of any triangle is 180 degrees. Suppose that one angle is a triangle has a degree measure of 10x-7 and another has a defree measure of 9x-5. Write an expression for the degree measure of the third angle in the triangle 

Answer 1

Let y = measure of third angle

 

"sum of the angle measures of any triangle is 180 degrees"    means

   (measure of first angle)  +  (measure of second angle)  +  (measure of third angle)  =  180

       (10x-7)                     +        (9x-5)                          +                y                     =  180

 

y = 180 -(10x-7) - (9x-5)

y = 180 -10x + 7 - 9x + 5

y = 192 - 19x