**Riddle**.

9. Three friends with economic difficulties share a coffee that costs 30 coins , so everyone puts 10 .

When you go to ask for a discount and pay the owner cut them 5 coins each taking a penny and leaving on a common background.

Later accounts do and say,

Each has paid nine coins have spent so 9x3 = 27 coins with both the background make 29 where the coin is missing ?

**Solution**

No missing coin, there is only one miscalculation , the two coins fund should not add them to the amount paid , but subtract the correct operation would be 9x3 = 27 coins paid 27-2 = 25 coins worn.