Using elimination method:

4x+2y=16 * 6 --> 24x +12y=96 ... eqn iii

6x-2y=4  * 4 --> 24x - 8y = 16 ... eqn iv

Subtract eqn iv from iii

20y = 80

y = 4

Subst. y for 4 in 4x + 2y = 16

--> 4x + 2(4) = 16

--> 4x = 16 - 8

--> 4x = 8

--> x = 2

: The value of (y-x) is 4 - 2 = 2