Question

fifteen years from now ravi's age will be four times his present age. find Ravi'S present age.

Answer 1

let x be ravi's present age.
x+15=4x
x-4x=-15
-3x=-15
x=-15\-3
  =5

Answer 2

let ravi's present age be x
then after 15 years
15+x=4x
4x-x=15
3x=15
x=15/3=5

check
15+5=20
4*5=20