$74/10 books equals $7.40 per book. If they want to mark them up at 25%, then that's 1.20 x (7.40), or $$8.88 selling price per each book
Another way you can do it is $7.40*the 20% markup and add that on top of the price per book $7.40*.20 = 1.48
$1.48+$7..40 = $8.88