SOLUTION: How would you solve this? Mary is presently 12 years older than her sister. Four years ago she was twice as old. How old are they now?

Question 978540: How would you solve this? Mary is presently 12 years older than her sister. Four years ago she was twice as old. How old are they now?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
How would you solve this? Mary is presently 12 years older than her sister. Four years ago she was twice as old. How old are they now?
--------
Equations:
m = s + 12
m-4 = 2(s-4)
-------
Substitute for "m" and solve for "s":
s+12-4 = 2s-8
s = 16 yrs (sister's age now)
--------------
Solve for "m"::
m = s + 12
m = 16+12 = 28 yrs (Mary's age now)
-----------
Cheers,
Stan H.
-----------
RELATED QUESTIONS
four years ago SOPHIE WAS twice as old as her sister. right now she is 1.5 times older... (answered by josmiceli)

john is presently 12 years older than fred. four years ago john was twice as old as fred. (answered by london maths tutor)

John is presently 12 years older than Joseph. Four years ago John was twice as old as... (answered by josmiceli)

John is presently 12 years older than Fred. Four years ago John was twice as old as Fred. (answered by macston)

Please help me solve this problem: John is as twice as old as Mary today. Three years... (answered by ankor@dixie-net.com)

Caridad is 6 years older than her sister. Four years ago she was 4 times as old as her... (answered by drj)

Caridad is six years older than her sister. Four years ago she was 4 times as old as her... (answered by ptaylor)

amie is six years older than her sister. Eiht years ago she was four times as old as her... (answered by Maths68)

Three years ago my brother was twice as old as my sister. Now he is 12 years older than... (answered by josgarithmetic,greenestamps)