7. Straight lines are also = to 180°
If you look at the diagram, when you add the two angles together, they form a straight line.
Since the angles add up to 180°, you can do:
(x + 25)° + (4x + 5)° = 180°
x + 25 + 4x + 5 = 180 Combine like terms
5x + 30 = 180 Subtract 30 on both sides
5x = 150 Divide 5 on both sides
x = 30
