\(\dfrac{2}{5} = \dfrac{?}{50} \Rightarrow ? = \dfrac{2 \times 50}{5} = 20\)... The answer key gives B (10). Re-checking: \(\dfrac{2}{5} = \dfrac{?}{50}\). Cross-multiplying: \(? = 20\). If the second equation is \(\dfrac{?}{5} = \dfrac{2}{?}\), then \(?^2 = 10 \Rightarrow ?\) does not simplify to 10 either. Answer key says 10 — verify the original question statement from the paper.