The expression $1.25p + $3.50 can be used to calculate the total charge for printing p pages at a business service store. how much would it cost to print 8 pages

Since one page cost $1.25 to print take the cost of per page $1.25 times the number of pages to be printed, in this case eight. $1.25 x 8 = $10.00
Remember there is still a $3.50 added to the cost of the pages printed; thus you have $10.00 + $3.50 = $13.50 which is the total charge.