How many different ordered pairs (x,y) of positive integers satisfy the equation above?
A pretty good, low-impact way to go here is to use the TABLE function on your graphing calculator.
Barring that, though, you can also get this one by plugging in small positive integer values for x and seeing what happens with y. When x = 1, y = 7. That works. When x = 2, y = 4. That works. When x = 3, y = 1. That works. When x = 4, y = –2. That doesn’t work. Because this is a linear equation and the graph won’t change directions, we know that no other ordered pairs will work.