The answer is going to be 15 nights
Since it gave us the duration of study by Nisha for the spelling bee=5 hours
We need to rate of her study which is=1/3 hour per night
Let she studies y hours for the spelling bee
Then we need to rate of her study=5/y which will divide hours of study by y
5/y=1/3
y=5(3)
y=15hours
Therefore she will have to study 15 nights.
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