Question

five years ago, a man was seven times as old as his son, while five year,hence the man will be four times as old as his son. find their present age

Answer 1

let the present age of man be x and that of his son be y
a/q
x-5=7(y-5)
= x-5= 7y-35
= x-7y= -30------(!)
again,
x+5=4( y+5)
x-4y=15------(!!)

(!!) -(!)
x-4y =15
x-7y=-30
- + +
----------------
3y =45
----------
y = 15 yrs
substitute y=15 in --(!!) ,we get

x-60 =15
x= 75yrs