Question 814892
Mrs. Jones is 28 years old now, so in three years she'll be 30. If, when she will be 30 she will be 3 times as old as her son, one-third of 30 is 30/3=10.
So in three years her son will be 10 years old.
Right now though, her son is 3 year's less than 10 years old, 10-3=7, so he is 7 years old right now.