8 lbs. We have 2 lbs for every 5 pies so the first step is to find out how many sets of 5 we have. We find this out by dividing 20 by 5. 20 divided by 5 is 4, so we have 4 sets of 5. If for every one set, we need 2 lbs of apples, we need to multiply the number of sets by 2. 4*2 is 8, so 8 is our final answer.