Kavita can complete a piece of work alone in 12 hours, while Komal can complete the same work alone in 18 hours. Kavita works alone for the first 4 hours and leaves. After that, Komal comes and completes the remaining work by herself. How much time did Komal take to finish the remaining work?

Let's assume the total work is 36 units.

Kavita can complete a piece of work alone in 12 hours.

Efficiency of Kavita = $$\frac{36}{12}$$ = 3 units/hour

Komal can complete the same work alone in 18 hours.

Efficiency of Komal = $$\frac{36}{18}$$ = 2 units/hour

Kavita works alone for the first 4 hours and leaves. After that, Komal comes and completes the remaining work by herself.

Let's assume the time taken by Komal to complete the remaining work by herself is 't' hours.

time of Kavita $$\times$$ Efficiency of Kavita + time of Komal $$\times$$ Efficiency of Komal = 36

$$4\times 3 + t \times 2 = 36$$

12 + 2t = 36

2t = 36 - 12

2t = 24

t = 12 hours

So Komal will take 12 hours to finish the remaining work.