Description: Sal shows how to complete the equation 4(x - 2) + x = 5x + _ so that it has infinitely many solutions. Created by Sal Khan. So first, my brain just wants to simplify this left-hand side a little bit and then think about how I can engineer the right-hand side so it's going to be the same as the left no matter what x I pick. And that's, of course, going to be equal to 5x plus blank. And that's going to be equal to 5x plus blank.*Teacher Advisor is 100% free.