I understand the concept of a surjective or onto function (to a degree). I understand that if the range and domain of the function are the same then the function is onto. My professor gave an additional definition which I did not understand. Here it goes: [itex]\forall[/itex]y[itex]\in[/itex]B [itex]\exists[/itex]x[itex]\in[/itex]A: f(x) = y I understand that I need to solve the equation for x, but once I solve the equation for x, what is the next step. How do I use that to demonstrate the function is surjective? Could you provide a function of your choosing and work out a problem, please?