What is the difference between mechanical digestion and chemical digestion in the mouth

Mechanical digestion is chewing, and chemical digestion is the saliva in your mouth breaking down food.

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