What is the justification for step 3 in the solution process?

Answer this question, only if you know the answer. 30 points and brainliest!

Does the point (1, sqrt 7) lie on circle shown.

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