55 divided by 5, divided by 5 divided by 5

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

Me n o w. i need t h i s. 10 points

Which radical expression is a rational number? a. √ 360 b. √ 644 c. √ 225 d. √ 122