One way to see if the graph is a function or not is by seeing if there is one output for every input. If the graph of the line touches a vertical line more than once, it is not a function, as this means there are two outputs for an input. For example, if a graph has a points that say (7,5) and (7, 10), the graph is not a function as 7 repeats more than once. Hope this helped!
