Joan is 15 years older than her brother Bill.Eight years from now,Joan will be twice as old as Bill.How old is each at this time?

Answer 1

J = B + 15

J + 8 = 2(B+8)

Substitute B+15 for J in the second equation and solve for B. Insert that value into the first equation to solve for J. Check by putting both values into the second equation.