One feeding trough has a width of 36". Another feeding trough has a width of 96". What is the percentage difference between the widths of the two troughs?

96-36 = 60

so 60/96 * 100% = 62.5%

Percentage difference is always relative to one of the items.

I. e. the factors are either 36/96 or 96/36.

If the reference is the 96" width, then difference is 96-36=60, and the percentage difference is 60/96=5/8=0.625 or 62.5%

If the reference is 36" (yes, usually the first mentioned item), the difference is still 60, but the percentage difference is 60/36=5/3=166.7%