Which expression has a value greater that 4 3

Can someone check if i did this right since i really want to make sure it’s correct. if you do you so much

What is the measure of ac? 5 units 13 units 26 units 39 units 3x- 2b 6x + 9

Jada has a meal in a restaurant she adds up the prices listed on the menu for everything they ordered and gets a subtotal of $42.00. when the check comes, it says they also need to pay $3.99 in sales tax. what percentage of the subtotal is the sales tax