Can you me do the steps for this geometry problems ?

How do you use the elimination method for this question? explain, because i really want to understand!

Determine which expressions represent real numbers and which expressions represent complex number. asaaap! plis!

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