[tex](7x + 40) + (6x + 43) = 180\\7x + 40 + 6x + 43 = 180\\7x + 6x = 180 - 40 - 43\\13x = 97\\x = \frac{97}{13}[/tex]
I'm not sure what you mean by Z but x is [tex]\frac{97}{13}[/tex]
