SOLUTION: Yolonda has 7 more baseball cards than Jeff. Jeff has three times as many baseball cards as Clara. All together, they have 21 baseball cards, how many does Clara have?

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Question 1152110: Yolonda has 7 more baseball cards than Jeff. Jeff has three times as many baseball cards as Clara. All together, they have 21 baseball cards, how many does Clara have?
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
y, Yolanda
j, Jeff
c, Clara

system%28y=j%2B7%2Cj=3c%2Cy%2Bj%2Bc=21%29


More than one way to go.

You could try sub for j.
system%28y=3c%2B7%2Cy%2B3c%2Bc=21%29

3c%2B7%2B3c%2Bc=21
7c%2B7=21
c%2B1=3
highlight%28c=2%29

Answer by ikleyn(52781) About Me  (Show Source):
You can put this solution on YOUR website!
,

Let x be the number by Clara; 

then the number by Jeff is 3x  and the number by Yolonda is (3x+7).


The equation is  


    x + 3x + (3x + 7) = 21.


Simplify step by step and solve


    7x = 21 - 7

    7x = 14

     x = 14/7 = 2.


ANSWER.  Clara has 2 baseball cards.

Solved.

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Never even try to solve this simple problem (and other similar problems) in a way as @josgarithmetic teaches you.

His way is the way to   N O W H E R E.

The problem is  extremely simple,   and the solution method/methods should be adequately simple.