Mathematics

Problem

Parallel lines

r

and

s

are cut by a transversal. One consecutive interior angle measures

(5y - 15)^\circ

and the other measures

125^\circ

. Determine the value of

y

. a)

28

14

10

12

Intuitive explanation

Consecutive interior angles (also called co-interior or same-side interior angles) are supplementary when formed by parallel lines and a transversal—they always sum to $180°$ . Set up an equation adding the two angle expressions and solve for $y$ ; this is a direct application of the parallel lines theorem that locks in the relationship between these angles.

Intuitive explanation

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