Question 257187
Mary was 4 times as old as Ann 10 years ago.if she is now twice as old as Ann, how old is mary

Let M be Mary's age today. Let A be Ann's age today.

Then we have:

1) M-10 = 4*(A-10) and
2) M = 2*A  or A = M/2 

Substititute A= M/2 in the first equation and solve for M.