11=r/13 solve and write division equitation

Eileen purchased 3.4 pounds of apples at the total cost of $19.72. if she purchases 6.2 pounds of apples at this store, how much would it cost?

Ineed someone to me answer my question i have to have this done and knocked out

1) prove that 731^3−631^3 is divisible by 100 2) prove that 99^3−74^3 is divisible by 25