Six dice with upper faces erased are as shows.

The sum of the numbers of dots on the opposite face is 7.

If even numbered dice have even number of dots on their top faces, then what would be the total number of dots on the top faces of their dice?

18

Even numbered dice are: (II), (IV) and (VI)

No. of dots on the top face of (II) dice = 6

No. of dots on the top face of (IV) dice = 6

and No. of dots on the top face of (VI) dice = 6

Therefore Required total = 6 + 6 + 6 = 18