Ages of Jack and Jill

Jack is three years older than Jill. Three years ago, Jill's age was four-fifths of Jack's age. How old is each now?

---

x = Jill’s age now
x + 3 = Jack’s age now   {Jack is three years older than Jill}

x - 3 = Jill’s age three years ago
​x = Jack’s age three years ago   {subtracted three from current ages}

x - 3 = (4/5)x  {three years ago, Jill's age was four-fifths of Jack's age}
5x - 15 = 4x {multiplied entire equation by 5 to eliminate fraction}
x = 15   {subtracted 4x and added 15 to each side}
x + 3 = 18   {substituted 15, in for x, into x + 3}

Jill is 15
Jack is 18

Ask the House

Leave a Tip