A proportional change means that for every change in 1 value, it is accompanied by a change in another value that is the same every time. For example, with this, if x=1 then y=2*1=2. If we move x up 1 value to 2, y=2*2=4. Next, if we move x one more value up then 3*2=y=6. As you may notice, y adds up by 2 every time. In addition, you multiply the x value by the same number every time and only that number (no adding anything) and it is therefore a proportional equation