Any help would be great

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

Solve the triangle. a = 21°, c = 105°, c = 5

Which expression is the factorization of x^2+10+21