The angles shown are supplementary, it means when we add them together, they add up to 180°:
[tex](5x + 3) + (x - 3) = 180[/tex]
Add like terms:
[tex]6x = 180 [/tex]
Divide both sides by 6 in order to isolate x:
[tex]x = 30[/tex]
The exterior angle is:
[tex]x - 3 = 30 - 3 = 27[/tex]
The interior angle is:
[tex]5x + 3 = 5 \times 30 + 3 = 150 + 3 = 153[/tex]
or[tex]180 - 27 = 153[/tex]
