Solution-
If the card replaced is the same which was drawn from the deck of card then the deck of card will be fair.
This is because initially the deck of card contains 52 cards having 4 suits containing 13 cards in each suit.
when one card is drawn then number of cards remained in the suit is 51 now the deck is incomplete.
when this drawn card is replaced in the deck of card the the deck again gets completed.
since the situation now for the deck of card is same as it was original, therefore the deck of card is fair.
If the card replaced is not the card which was drawn from the deck then in that case the deck will be unfair.