Ricky is 4 times as old as his sister, who's 5. How old will Ricky be when he's twice as old as her?

Answer 1

s = 5
R = 4 * 5 = 20

(5+x)2 = 20 + x
10 + 2 x = 20 + x
x = 10 years from now
20 + 10 = 30