Apharmacist has 40% and 80% iodine solutions in hand . how many liters of each iodine solution will be required to produce 6litere of a 50% iodine mixture

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