1) C 49.75
You just have to multiply by the percentage when it's a discount and subtract it from the original amount, 50% becomes .50. 99.50*.5=49.75 99.4-49.75=$47.75
2) D 103.48
You multiply by the percentage (0.04) and then add it to the original price when it's a tax
3) D 4.74
The same process as tax multiply by percentage (.2) and add to the original price
The difference between a markup and tax is the store controls the markups while taxes are usually state-controlled on a certain product (soda 5c or 10c tax is by state)