A fathers age = three less than two times the son's age can be writtens as: f=2s-3. Since the difference in their age, f-s=30, we can solve for s and find that s=f-30. plugging this in to the first equation, we get f=2(f-30)-3 = 2f-60-3 =2f-63
f=2f-64
solvinh for f yields,
f=64
if thr father is 64, the son's age is therfore 64-30=34