Answer:
x = 28.75°
Step-by-step explanation:
First, you have to solve for the angle that is supplementary with 120°.
180° - 120° = 60°
The inside angles must add up to 180°, so the equation will be:
(3x+5)° + x° + 60° = 180° ––Now combine like terms (the x's)
(4x + 5)° + 60° = 180° ––Combine the like terms on the left (5 and 60)
4x° + 65° = 180° –– Get the x term all alone by subtracting 65 from both sides
4x° = 115° –– Divide both sides by 4 to get x by itself
x = 28.75°
Check by substituting:
[(3•28.75)+5]° + 28.75° + 60° = 180
(86.25 + 5)° + 28.75° + 60° = 180°
91.25° + 28.75° + 60° = 180°
120° + 60° = 180°
180° = 180°
This is correct.
