## Algebra: A Combined Approach (4th Edition)

Answer: - $c$. Less than 5 hours.
The reason is very simple, The second person alone can complete the job in 5 hours. So if he has help for his work, they both will complete the work in less than 5 hours. We can check this too: Work done by first person in one hour. $\frac{1}{7}$ Work done by second person in one hour. $\frac{1}{5}$ Let the work done $both$ of them in one hour = $\frac{1}{x}$ Thus, $\frac{1}{7}$ + $\frac{1}{5}$ = $\frac{1}{x}$ Thus, $\frac{5+7}{5(7)}$ = $\frac{1}{x}$ $\frac{12}{35}$ = $\frac{1}{x}$ Thus x = $\frac{35}{12}$ = 2$\frac{11}{12}$ hours.