Question

Sarah is 25 years older than her son Gavin, In ten years, Sarah will be twice Gavin's age, How old are Sarah and Gavin now?

Answer 1

I found:
Gavin `15`
Sara `40`

Explanation:

Call the ages of Sara `s` and Gavin `g`, we get:
`s=g+25`
`s+10=2(g+10)`
substitute the first into the second for `s`:
`(color(red)(g+25))+10=2g+20`
rearrange:
`g=15`
back into the first:
`s=15+25=40`