It could be either, we need more info. How big are each? If it doesn't say, then it's a trick question. Throw Schrodinger's cat at it or something.
First, you must understand the question. what % of 60 is 15, so I would write an equation to express this.
15 = 60x
From there, solve for x, so Divide by 60 on each side. The answer is 1/4, or 25%
There are 96 possible combinations.
The fundamental counting principle states that the number of total options is given by multiplying the number of possibilities for each option, or
Total choices = choices x choices x ...
4*3*8 = 96
1 pound = 16 oz
Her books weigh 9 pounds or (9)(16)= 144 oz
Math Textbook= 40 oz
Biology textbook= 3 pounds or (3)(16)= 48 oz
Total weight of books - math textbook - biology textbook = science textbook
144-40-48 = 56oz
science textbook = 56oz
