Answer:
Option 3: 12 is the correct answer.
Explanation:
Given functions are:

In order to find the value of x on which (f-g)(x) will be zero, first of all we have to find (f-g)(x) and then equate it equal to zero to find the value of that will make (f-g)(x)
So,

Now to find the value of x on which (f-g)(x) will be zero, putting (f-g)(x) = 0

Adding 24 on both sides

Dividing both sides by 2

For x=12, (f-g)(x) will be zero.
Hence,
Option 3: 12 is the correct answer.