How many isotopes can an element have?

 The element with the greatest number of known stable isotopes is tin, with 10 stable isotopes. Including unstable isotopes, mercury, cesium, and barium are each known to have 40 isotopes. Theory predicts however that many unstable isotopes should exist which have not yet been discovered (especially on the neutron-rich side of the line of stability.)

If one were to put the y value into the equation, they could find out what x is for a certain value of y.  putting in the value of y (1), we get the equation: 1=4x-12=4xx=0.5this means that the value of x when why is 1 is x=0.5