Allison practices her violin for at least 12 hours per week she practices for three fourths of an hour each session if allison has already practiced 3 hours this week how many more sessions remains for her to meet or exceed her weekly practice goals.

At least 12 more sessions 

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.