Posted by mm on Friday, April 15, 2011 at 8:35am.
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?

math  bobpursley, Friday, April 15, 2011 at 8:44am
M=16
M=4B
(M+t)=2(B+t)
so B= 4, then
M+t=8+2t
8=t
so mary will be 16+8=24, brother 12, now Mary is 16, brother is 4