{x | x is a multiple of 2} ∪ {x is a multiple of 7}?
Multiple of 2 = 2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,
32,34,36,38,40,42,44,46,48,50 etc
Multiple of 7 =
7,14,21,28,35,42,49,56,63,70 etc
So x = 14,28,42,56,70,84,etc
You should know the needed x values because you did not mention the range of x