Answer :
before we start the math you must know that he is trying to beat his record so we cant do 72-10 lets do 73 instead because that is the least he can eat to beat his record so first do 73-10 that is 63 now he only has 9 min left to eat 63 more hot dogs just do 63/9 and that gets you 7 he must eat at least 7 hot dogs every min for 9 min to beat his record