Parallel lines and angles with algebra

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Learn it With parallel lines, corresponding (F) and alternate (Z) angles are equal; co-interior (C) angles add to 180°. Set up an equation from the right rule, then solve for x.

Example: Alternate angles are $(3x + 10)°$ and $(5x - 30)°$.

Alternate angles are equal: $3x + 10 = 5x - 30$.
$40 = 2x$, $x = 20$.
Each angle is $3(20) + 10 = 70°$.

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