What is davison and subtraction

When you have an equation you need to solve use pemdas. P stands for parenthesis so that would be your first step. E stands for exponents that would be your second step. M stands for multiply that is your 3rd step. D stands for division that would be your 4th step. A stands for add that would be your 5th step. S stands for subtract that would be your 6th step. Using pemdas helps you solve equations correctly. If you can’t remember pemdas then remember “Please Excuse My Dear Aunt Sally.”

$7.50x+$4.50y=midk it's been awhile since i've done one of these