Question 753887: Jeff is 7 years older than Marty. The sum of their ages is 71. How old is Marty
Found 2 solutions by ankor@dixie-net.com, MathTherapy:
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! Write an equation for each statement
:
Jeff is 7 years older than Marty.
j = m + 7
or
j - m = 7
:
The sum of their ages is 71.
j + m = 71
:
Use elimination here, add the two equations
j - m = 7
j + m = 71
------------adding eliminates m, find j
2j = 78
j = 78/2
j = 39 is Jeff's age
:
How old is Marty? I'll let you find this
Answer by MathTherapy(10552)  (Show Source):
You can put this solution on YOUR website!
Jeff is 7 years older than Marty. The sum of their ages is 71. How old is Marty
Let Marty's and Jeff's ages be M, and J, respectively
Then: J = M + 7 ----- eq (i)
Also, J + M = 71 ------ eq (ii)
While a few methods can be used to solve this system, namely, substitution, elimination, graphing, etc., the easiest method HERE is that of substitution.
M + 7 + M = 71 ------ Substituting M + 7 for J in eq (ii)
2M = 64
M, or Marty's current age =  , or 
You can do the check!!
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