The first cylinder: It is said that the second cylinder is now 5/7 of the first cylinder, so if you divide it by 5/7, you get 70 yuan (plus the original 15 yuan for the first cylinder, it is 85 yuan (original)).

Second cylinder: (original) 50- 15=35 tails (minus the second cylinder)

The first cylinder has 50 more tails than the second cylinder (85-35==50).