Ineed finding out the answers for questions a, b, c, and d.
it says i need to identify a variable and write an equation for each
i don't really understand.

The major difference is that a histogram is only used to plot the frequency of score occurrences in a continuous data set that has been divided into classes, called bins.  bar charts, on the other hand, can be used for a great deal of other types ofvariables  including  ordinal  andnominal  data sets.

Here is my answer, i'm sorry if you didn't understand my explanation