How to be good at math???

Write two subtraction equations that are equivalent to 5 + 12 = 17.

Find the center and the radius of the circle with the equation: x^2-2x+y^2+4y+1=0?

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