In the sequent you have positive and negative numbers, so the formula must switch the signs. You can do that with multiplication with - (to switch sign in every next step. +*-=-, -*-=+)
divide the original price by 2 since it is half off. that gives you 6.44. so you would multiply 6.44 by 5, since allison wants 5 cases. that gives you 32.20 dollars
