Question

Today the age of Sam is five times the age of Sally. After 21 years, Sam will be twice as old as Sally. Find their present ages.

Answer 1

Let the age of Sam be x and Sally be y
$x=5y$
After 21 years their ages will be x+21 and y+21
$(x+21)=2(y+21)$
$(5y+21)=2y+42$
$3y=21$
$y=7$
$x=5y=5\left(7\right)=35$
$\therefore$ Age of Sam = 35 and age of Sally = 7