Y varies jointly as the square of x and the square root of z. When x = 2 and z = 9, then y = 24. Find y when x = 3 and z = 25.

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

Hi, can anyone show me how to do this problem? 100 points for this. in advance

Write the percent as a fraction or mixed number in simplest form. 0.8%