Question 1005144
Call the father and son's age NOW, f and s.  Then we have
f = s + 28  and
f - 10 = 15(s - 10)
Substitute the first into the second equation and get
s + 28 - 10 = 15(s - 10)
s + 18 = 15s - 150
168 = 14s
s = 12
f is then 40