you always combine your like terms, a trick is to put a line infront of your equation signs making it look like 3x/+2y/+5x/-y. This makes it easier to see if your terms are positive or negative. Now you have 5x+3x and 2y-y giving you 8x+y because its still positive.
She may have used a wrong operation to get this answer. 73 is not the correct answer, and you can prove it using a calculator or longhand. The correct answer is 6888.
