Question

Will is twice as old as Jill. Three years ago, Jill's age was two fifths of Will's age then. How old is each now?

Please show how you solved this problem

Answer 1

"Will is twice as old as Jill."

                       Jill's age . . . . .   J
                       Will's age . . . . 2J .

"Three years ago . . .

                       Jill's age then . . . . .   J - 3
                       Will's age then . . . . 2J - 3

". . . Jill's age then was 2/5 of Will's age then."

                                         J - 3  =  (2/5) (2J - 3)
Multiply
each side by  5 :          5J - 15  =  2 (2J - 3)

Divide
each side by  2 :          2.5 J - 7.5  =  2J - 3 

Subtract  2J
from each side:            0.5 J - 7.5  =      -3

Add  7.5
to each side:                0.5 J           =     4.5

Multiply
each side by  2 :                J            =       9

Jill is  9  y.o. now.
Will is 18 y.o. now.