Technically you'd get a compile error, due to the absence of a semi-colon after the forth statement (x = y z * 2; is invalid). Additionally, z * 2; is an invalid statement, as all programming languages that I know require you to specify the new value of z, such as (z = z * 2) or (z *= 2).
If we assume there's a semi-colon there, then the value of x after the following statements would be 5, as we are setting x's value to the value of y (which is 4), and x is never again modified in those statements.