Let x represent Ravi's current age.
Now, Ravi's age fifteen years from now is effectively Ravi's age plus fifteen, therefor we can write this as x + 15.
Four times Ravi's present age is four multiplied by his present age, therefor we can write this as 4x.
If Ravi's age fifteen years from now is equal to four times his present age, then:
x + 15 = 4x
Now all we have to do is solve for x to find Ravi's present age:
x + 15 = 4x
15 = 3x (Subtract x from both sides)
5 = x (Divide both sides by 3)
Therefor, Ravi's present age is 5 years.