well, if the total number of oranges is say "o", and the total number of grapes is "g", then (1/3)o were spoiled and (1/4)g were also spoiled, and we happen to know that it was 4 and 7 respectively, thus
[tex]\bf \cfrac{1}{3}o=4\implies \cfrac{o}{3}=4\implies o=3\cdot 4\implies \boxed{o=12}\impliedby total
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\cfrac{1}{4}g=7\implies \cfrac{g}{4}=7\implies g=4\cdot 7\implies \boxed{g=28}\impliedby total\\\\
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\textit{so, there were then }12+28\textit{ pieces of fruit in the basket}[/tex]
