Plz help. Will give brainliest to right answer. Need by 9:20

If f(x)=-x^2+6x-1 and g(x)=3x^2-4x-1,find(f+g)(x)

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

How do i multiply two digit numbers