if you buy x of these items for 8 dollars each, then 8*x represents how much you've spent so far. If you start off with $60, then 60-8x = -8x+60 is the total amount of money leftover in your pocket.
If you start off with $60 and end up with $28, then -8x+60 = 28 is the equation that models this. Solving for x leads to finding out how many of these items you have purchased. In this case, the solution is x = 5.
