Given the task definition and input, reply with output. You are given a math word problem and you are supposed to apply multiple mathematical operators like addition, subtraction, multiplication or division on the numbers embedded in the text to answer the following question and then only report the final numerical answer.

Luke had 20 stickers . He bought 12 stickers from a store in the mall and got 20 stickers for his birthday . Then Luke gave 5 of the stickers to his sister and used 8 to decorate a greeting card . How many stickers does Luke have left ?
39