Ratio and Proportion

Concept:The ratio condition holds for any common multiplier, so the exact earnings cannot be determined.Explanation:Let A's earnings be $4k$ and B's earnings be $7k$.After a $50\%$ increase, A becomes $4k \times 1.5 = 6k$.After a $25\%$ decrease, B becomes $7k \times 0.75 = 5.25k$.The new ratio is $6k : 5.25k = \frac{6}{5.25} = \frac{8}{7}$.This matches the given ratio $8:7$ for any positive $k$.Thus, $k$ can be any positive number, so A's earnings ($4k$) cannot be uniquely found from the data.Answer:Data inadequate