Pipe A can fill a tank in 12 hours. Pipe B can empty it in X hours. If both the pipes are opened together, then the tank 4 will be filled in 30 hours. Find X.

Correct option is A

The rate of work done by Pipe A (filling rate) = 1/12 (since it fills 1 tank in 12 hours). The rate of work done by Pipe (emptying rate) = 1/X (since it empties 1 tank in hours).
When both pipes are opened together, the net rate of work is:
1/12 - 1/X
Given that the tank fills in 30 hours, the rate of filling is: 1/30
Step 2: Form the Equation
1/12 - 1/X = 1/30
Multiply by LCM(12,X,30) to clear fractions: Taking LCM of 12,X, and 30 , we get 60 X . Multiply the whole equation by 60 X :
1/12 × 60X - 1/X × 60X = 1/30 × 60X
5X – 60 = 2X
5X - 2X = 60
3X = 60
X = 20