The new dolphin tank at the city aquarium is in the shape of a rectangular prism. It is 23yd long by 15yd wide by 4yd deep. To make the tank livable for the dolphins, the aquarium workers treat the water using bags of salt. The amount of water a bag of salt can treat is known in cubic feet.

If x<0 and y>0, then the sign of the real number x-y/xy would be positive. If x is negative and y is positive then x-y is negative and xy is negative. A negative number  divided by another negative number would be positive. Hope this answers the question.