Alocal concert promoter purchases 2 3/4 od ads when one of the concerts is canceled the promoter cancels 1 5/8 pages of ads how much advertising space is the concert promoter actually using?

In this question it is given that the promoter first purchased 2 3/4 of ads at first. When one of the concerts got cancelled, then the promoter cancels 1 5/8 pages of ads. It is required to be found the number of pages the promoter is using finally.
Number of pages bought by the concert promoter initially = 2 3/4
                                                                                             = 11/4 pages
Number of pages cancelled by the promoter
after one concert got cancelled = 1 5/8
                                                   = 13/8 pages
Then the total number of pages finally used by the promoter = (11/4) - (13/8)
                                                                                                 = (44 -13)/8
                                                                                                 = 31/8
                                                                                                 = 3 7/8 pages
So the total amount of space used for ads by the concert promoter is 3 7/8 pages.