Please help I have a test

Let w=23 . what is the value of w + 45 ?

If f(x)=2x-6 and g(x)=3x+9, 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