2x - y = 8
x + 3y = 4

x = 4, y = 0

Step-by-step explanation:

Two find x and y, we can simply solve one of the two equations for one of the variables, and substitute it into the other.  That will provide one of the two values, which can then be plugged into either equation for the other value.  Let's do it:

So x is equal to four, and y is equal to zero.