SOLUTION: Michelle is 21 years older than her brother Frank. Nine years from now, Michelle will be twice as old as Frank. How old is each at the present time?

Question 1030858: Michelle is 21 years older than her brother Frank. Nine years from now, Michelle will be twice as old as Frank. How old is each at the present time?
Found 2 solutions by fractalier, josmiceli:
Answer by fractalier(6550) (Show Source): You can put this solution on YOUR website!
Call their ages NOW, m and f. Then we write
m = f + 21
Nine years from now,
m + 9 = 2(f + 9)
Substitute the first one into the second and get
f+21 + 9 = 2(f + 9)
f + 30 = 2f + 18
Now subtract 18 and subtract f and get
f + 12 = 2f
f = 12
Thus Michelle is 33.
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = Michelle's age now
Let = Frank's age now
------------------------------
(1)
(2)
-------------------------
Substitute (1) into (2)
(2)
(2)
(2)
(2)
and
(1)
(1)
(1)
Michelle is 33 and Frank is 12
--------------------------
check:
(2)
(2)
(2)
(2)
OK
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