Where is $1?

[Yozuvchi]

3 friends in the restaurant:
they ate and the total amount of their bill is $25.
Three of them paid $10 each.
The waiter returned $5.
They could not divide $5 into 3, so they returned $2 to waiter as a tip, and didived $3 between themselves.

So, now if we look back, they paid $9 each (10-1). 3x9=$27 and if we add up the tip amount of $2, the gross amount becomes $29.

Where is $1?

[trigger-happy]

So, now if we look back, they paid $9 each (10-1). 3x9=$27 and if we add up the tip amount of $2, the gross amount becomes $29.

Nope. The bill was $25 + $2 tip = $27. Plus the $3 they split from the change the waiter gave them. $27+$3 = $30. Divide by 3, you get $10. It's all there! ;)

[Yozuvchi]

Trigger-happy, your answer is correct! Bravo! But let me put the clear answer:

Actually they do not need to add $2 to their $27 in order to try to get $30.
They paid $9 each which makes $27 for 3 people. The bill is $25. So they paid $25 for the bill and $2 as a tip. So, they should subtract $2 to get $25.

The change of $3+(bill amount $25+$2 tip or) $27 = $30/3 = $10