Sir, if gift is given by mother to son ,then in son capital a/c its gift received,as it same in case of mother?

Generally, the capital account of mother is subtracted/reduced by that amount, but it remains on left side (Liability) of Balance sheet only.

And Son's capital gets incresed to that effect.

Sir,

Then what should i do whether deducted in the capital account of mother or show in left side liabilities in balance sheet.

You can reduce the capital account of mother upto the amount of Gift given. (actually a journal entry is to be passed)

ok sir, actually mother has paid Rs 300000 directly to car dealer ,and car is purchase in the name of son.So this be assume as a gift as mother has gifted this amount.