There are two points in the set that have the same x-value or "input": (6,4) and (6,-4). This fails the vertical line test which means that one input will give two potential outputs. This cannot make a function.
if we divide the 15 water bottles by 5 we get 3 water bottles. This is how many she took so following the same scale factor we would then divide 20 by 5 and get 4.
