The ratio John's age to Ryan's age is 3:1 now . 25 years later , the ratio will become 4:3 .How old is John now ?

j:r = 3:1, so j=3r

(j+25)/(r+25) = 4/3
(3r+25)/(r+25) = 4/3
3(3r+25) = 4(r+25)
9r+75 = 4r+100
5r = 25
r = 5

so, John is 15
in 25 years, the two will be 40 and 30