Answer:
x = 12
Explanation:
For this problem it is important to note that the sum of the two unknown angles' measurements is equivalent to the given known angle measurement as implied by the drawing. With this in mind let's write our givens:
m<CGF = 10x - 10
m<HGC = 3x + 10
m<HGF = 156
So now let's form our equation to represent the drawing:
m<CGF + m<HGC = m<HGF
And now let's solve the equation to find the value of the x.
m<CGF + m<HGC = m<HGF
( 10x - 10 ) + ( 3x + 10 ) = 156
10x - 10 + 3x + 10 = 156
13x = 156
x = 12
Hence, our value for x is 12.
Cheers.