Answer:
son is 3 and mother is 23
Explanation:
let n be the son's age then mother is n + 20
in 7 years
son is n + 7 and mother is n + 20 + 7 = n + 27
the mother is then 3 times as old as her son , that is
n + 27 = 3(n + 7)
n + 27 = 3n + 21 ( subtract n from both sides )
27 = 2n + 21 ( subtract 21 from both sides )
6 = 2n ( divide both sides by 2 )
3 = n
that is the son is 3 years old and the mother is 3 + 20 = 23 years old