A can complete $$33\frac{1}{3}$$% of a work in 5 days and B can complete 40% of the same work in 10 days. They work together for 5 days and then B left the work. A alone will complete the remaining work in:

Let total work to be done be 75 units

=> A complete $$\frac{1}{3}^{rd}$$ of the work i.e. 25 units in 5 days, => A's efficiency = $$\frac{25}{5}=5$$ units/day

Similarly, B complete $$\frac{2}{5}^{th}$$ of the work i.e. 30 units in 10 days, => B's efficiency = $$\frac{30}{10}=3$$ units/day

=> Work done by them together in 5 days = $$(5+3)\times5=40$$ units

$$\therefore$$ Remaining work will be completed by A in = $$\frac{(75-40)}{5}=7$$ days

=> Ans - (C)