You are given a math word problem and you are supposed to apply a single mathematical operator 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.

for halloween frank got 15 pounds of candy . if he gave 8 pounds to nancy what 's the difference between the pounds of frank 's candy before he gave nancy and he gave to ?
7

a fast food restaurant had 91 hotdogs . after selling some they had 20 left . what 's the difference between the number of hotdogs before selling and after selling ?
71

another material that he needs is rope . if he already has 6 feet of rope and he needs additional ropes having 5 times the length of what he already have how long should be the additional rope ?
30