You purchase a $220 arline ticket. you have a discount code to receive 10% off. there is a 10.5% service charge added to the total. how much do you pay for your ticket

When you see % next to a number, you multiply it by .01.
10 becomes .1
10.5 becomes .105

220*.1=22, so this is the 10% off
220*.105=23.1, so this is the 10.5% service charge.

220-22+23.1=$221.10 for the ticket.