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Review: A Difference and a Total
Explanation
We can create variables B and G for the numbers
of boys and girls. The first phrase tells us that 
.
(We can pick numbers for a case to check that the 6 is on the correct side.)
The second phrase tells us that 
.
We want G. We can actually just add
these two equations to obtain 
.
The B's drop and 
.
The correct answer is (D).
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