Question 648959
 3/4 + ? = 9/14 
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3/4 + q = 9/14  (I replace the ? with q)
Subtract 3/4
q = 9/14 - 3/4
Find a common denominator for 4 & 14.
The product always works: 4*14 = 56
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q = 36/56 - 42/56
q = -6/56
q = -3/28