16Hit1600
Geometry and TrigonometryVery hardCo-interior angles on parallel lines

Geometry and Trigonometry practice question

Two parallel lines are cut by a transversal. Two interior angles on the same side of the transversal measure (3x + 10)° and (2x − 5)°. What is the value of x?

Answer: 35

Co-interior angles on parallel lines are supplementary: 3x + 10 + 2x − 5 = 180 → 5x = 175 → x = 35.

Common wrong answers

If you answered 15
15 comes from setting the angles equal, which is the rule for alternate angles, not co-interior ones.
If you answered 37
37 comes from 5x − 5 = 180.
If you answered 70
70 is 2x.

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