AP / PB = AQ / QC
8 / x = 12 / 18
8 / x = 6 × 2 / 6 × 3
8 / x = 2 / 3
Inverse both sides :
x / 8 = 3 / 2
Multiply both sides by 8
8 × x / 8 = 8 × 3 / 2
x = 2 × 4 × 3 / 2
x = 4 × 3
x = 12
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