Question

Mary, who is sixteen years old, is four times as old as her brother. How old will Mary be when she is twice as old as her brother?

Answer 1

32

Explanation:

16 times 4 is 64

64 divided by 2 is equal to 32

Answer 2

M = 16
16 = 4B
B = 4
(M - B) = 12 <== this will never change. Mary will always be 12 yrs older than he is.

So, when she is twice as old as he is, he is 12 and she is 24.
That will occur in 8 years from now.
They should live long and prosper.