According to the question, Bachal is now three times as old as his son,

so, x = 3y

five years before their ages would have been, x-5 and y-5. And the question says the Bachal was four times as old as his son,

x-5 = 4( y -5)

x-5= 4y -20

x-4y + 15 = 0

3y - 4y + 15 =0 , we already know x = 3y

y = 15 and x = 45

The Bachal is presently 45 and the son is 15