Logic/Algebra Problem

There is no mentioning of the father's age therefore you can not calculate the age of the father. You can get the ages of mother and the son but father is out of question.

Actually, I already knew the anwer.....X=21+Y because the mother is 21 years older than the son....X+6=5(Y+6) because in 6 years, the mom is 5 years older than the son....so (using substitution): 21+Y+6=5y+30 which simplifies to Y+27=5Y+30.....this further simplifies to -3=4Y....so: Y=-3/4 of a year....there are 12 months in a year....-3/4*12=-9....so: Age of the son equals -9 months....Where is the father? Inside the mother.