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Answer:
y = 170 -3x
Explanation:
The marked angles are called "same-side interior angles", or "consecutive interior angles" because they are between the parallel lines and on the same side of the transversal. Such angles are supplementary.
y + (3x +10) = 180
y = 180 -(3x +10) . . . . . subtract everything on the left that is not y
y = 170 -3x . . . . . . . . . simplify