Question 31068
Let's see if I've got this right.
The three men paid $10.00 each ($30.00) and were refunded $1.00 each ($3.00), so in effect, they paid $27.00 (3 X $9.00) as a group, right? So where's the $27.00?
Well, the seller has $25.00 and his son has $2.00.
So, $25.00 + $2.00 = $27.00 What missing dollar?

Another way to look at it.
The three men each paid $10.00 for a total of $30.00
Where's the $30.00?
The seller has $25.00.
The son has $2.00
The three men have $1.00 each or $3.00 altogether.
So, $25.00 + $2.00 + $3.00 = $30.00