A can do a certain work in the same time in which B and C together can do it. If A and B together could do it in 10 days and C alone in 50 days, then B alone could do it in:
Answer: C
Let their 1 day's work be A, B, C. Given A = B+C. Also, A+B=1/10 and C=1/50. Substitute C in the first equation: A = B + 1/50. Substitute this A into the second equation: \((B+1/50) + B = 1/10 \Rightarrow 2B = 1/10 - 1/50 = (5-1)/50 = 4/50 = 2/25\). So, \(B = 1/25\). B alone can do the work in 25 days.