GRE Sample Test 4 Quantitative Reasoning 2

Begin with cross multiplication and use algebra to isolate $\frac{\mathit{q}}{\mathit{p}}$.
$\frac{\mathit{p}-\mathit{q}}{\mathit{p}}$ = $\frac{2}{7}$
7(p − q) = 2p Cross multiply.
7p − 7q = 2p Remove parentheses.
5p = 7q Add 7q; subtract 2p on both sides.
$\frac{5}{7}$ = $\frac{\mathit{q}}{\mathit{p}}$ Divide both sides by 7p.
Choice (B) is correct.