1. suppose the university bursar said that 600 students entered for business mathematics, 300 entered for statistics while 173 students entered for both business mathematics and statistics. how many students enrolled in the two courses altogether?

My understanding is, we have 600 in BM, 300 In Stats = 900.
173 have enrolled in both, so they have been counted twice.  We can subtract that from the total, 900-173 = 727 unique students.

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.