SOLUTION: Shelia's age plus Kerry's age is 27 Shelia's age plus jack age is 38 Kerry's age plus jack age is 33 How old is jack?

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Question 1192644: Shelia's age plus Kerry's age is 27
Shelia's age plus jack age is 38
Kerry's age plus jack age is 33
How old is jack?
Found 2 solutions by ikleyn, josgarithmetic:
Answer by ikleyn(52776)   (Show Source): You can put this solution on YOUR website!
.
Shelia's age plus Kerry's age is 27
Shelia's age plus jack age is 38
Kerry's age plus jack age is 33
How old is jack?
~~~~~~~~~~~~~~~~~~~~ 

From the condition, you have these three equations 

    S + K = 27    (1)

    S + J = 38    (2)

    K + J = 33    (3)

-------------------------  Add equations (1), (2) and (3).   You will get


    2S + 2K + 2J = 27 + 38 + 33

    2S + 2K + 2J =      98


Divide both sides by 2

    S + K + J = 49    (4)


To find Jack age, subtract equation (1) from equation (4).  You will get then

            J = 49 - 27

            J =   22.


ANSWER.  Jack is 22 years old.

Solved.

-----------------

This problem is of very special class of problems.
They admit very special method of solution, which I showed you in this post.

It is worth to be memorized.



Answer by josgarithmetic(39616)   (Show Source): You can put this solution on YOUR website!
Sheila         x
Kerry          k
Jack           j



Add corresponding members.




Using equation 1 of the main system, and subtract from this highlited equation, will give the value for j.


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