My equations and these serial numbers overlap a liittle part.
How do I separate them with a small distance.
I show the overlapping in the picture I attached.
that's a known problem of eqnarray. eqnarray is obsolete, use the align environment of amsmath instead. For reasons and examples have a look at eqnarray vs. align. I modified your example:
You may see that the equations are automatically aligned at the = relation symbol, perhaps you like that. There should be no overlapping, the tag/number would be set into the next line.
Perhaps you want to use a smaller font in that case, try: