Answer:
3 inches
Step-by-step explanation:
The volume of a rectangular prism is the product of length, width, and height. Fill in the information you have in the formula, and solve.
... V = LWH
... 258 3/4 = (7 1/2)×W×(11 1/2)
... W = (258 3/4)/((7 1/2)(11 1/2))
This computation can be done using fractions, but it is probably more easily done using decimal numbers. Of course, you know that 3/4 = 0.75 and 1/2 = 0.5. Then ...
... W = 258.75/(7.5×11.5) = 3
The width is 3 inches.