Please help me with this homework

X2 + y 2 = 36 x + y = 6 solve the system of equations.

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 this problem! extra ! 3025/5.5 = a/90.75