What is the value of ..

Which is the equation of a line perpendicular to the line with the equation 3x+4y=8

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

Which property was used to simplify the expression? 3c+9 +4c=3c+4c+9