you add 30% to 100% to get 130% since it is a mark up, and then you convert to a decimal by going to the left twice then multiplying by original price.
PART B
Since it is a discount you subtract 15 percent from 100, but then add back 5 percent since there is tax applied to get 90%, convert to decimal and multiply by original price to get $88 x .9 = $79.20
