How do i convert 35 percent into decimal like for example you have 60 percent and convert it .06 how do i do that with 35 percent

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