Qus 1 : The peasant had 21 peso. As he crossed the bridge for the first time, it becomes (21X2) or 42 peso. He gave 24 peso to devil and left with (42-24) or 18 peso.
Now he crossed the bridge second time. His money becomes double (18X2) or 36 peso. He gave 24 peso to devil and left with (36-24) or 12 peso.
Now he crossed the bridge for third time. The money gets double and becomes (12X2) or 24 peso. He had to give the all to devil and left with no money.
Moral : Never fall in trap of the devil.

Qus 2 : The inn owner initially served 27 boiled potatoes. Each of the farmers were supposed to eat 9.
The first farmer found 27. Eaten (27÷3) or 9 and left (27-9) or 18. The second farmer found 18, eaten (18÷3) or 6 and left (18-6) or 12. The third farmer found 12, eaten (12÷3) or 4 and left (12-4) or 8. This is what they found when all are awake.
As they are supposed to eat 9 potatoes each, the second farmer (who had 6 potatoes earlier) can eat (9-6) or 3 out of the remaining 8 and the third farmer (who just had 4 potatoes) can eat (9-4) or 5 out of the 8 potatoes. The first farmer already eaten 9. However, they can now make a potato crush with remaining 8 potatoes, order a drink and have a party.
Moral : Always have your food together with your friends.

I have re-steemed this announcement. I'm inviting my friend @bull1 and @beautymondal to participate in this contest.