Answer :
-- After dog ate 1/2 of the collection, there were 29 remaining.
-- Just before dog came along, there were (2 x 29) = 58 cards.
-- That was after Dan added 5 new ones.
-- Before he added the 5 new ones, there were (58 - 5) = 53 cards.
-- When this story began, Dan had 53 cards.
first you double 29
than subtract the 5 new cards
29 x 2 - 5
58-5
your answer is 53