Sally's grandfather is 67 tears old.

Sally is 19 years old.
At what age will Sally be exactly one third of her grandfather's age?
How old will her granfather be then?

1 answer

( 67 + x ) / ( 19 + x ) = 3 Multiply blth sides by ( 19 + x )

67 + x = 3 ( 19 + x )

67 + x = 3 * 19 + 3 * x

67 + x = 57 + 3 x

67 - 57 = 3 x - x

10 = 2x

2 x = 10 Divide both sides by 2

x = 10 / 2

x = 5

Salys age will be 19 + 5 = 24

Granfathes age will be 37 + 5 = 72

72 / 24 = 3