Math
posted by Jonathan .
The sum of John's age and twice of his son's age is 56. In 8 years time, the son's age will be half of john's age. Find there present ages.
Right now I wrote down an equation x+2y=56 and not quite sure what to do next.

OK. That's the first sentence covered in x+2y=56 .
In 8 years time, the son's age will be half of john's age.
If x is John's age now, then his age in 8 years is (x+8), and his son's will be (y+8).
So the next thing is to make a second equation from that sentence, using (x+8) and (y+8) for the ages. 
x=20 and y=18