No it is an irrational number
In order to figure out what number 1500 is 5% of, take 1500 and divide it by 5% (0.05). The answer is the salesman would have to sell $30,000 to make $1500 in commission.
Unit cost of a ticket = Income from ticket sales / number of tickets sold:
$1250
--------------- = $6.58 per ticket
190 tickets
Again:
$1175
--------------- = $6.71
175 tickets
While ticket prices do change (usually increase) from year to year, it's unusual to see such a situation here.
Don't have any guidelines by which to determine the "fixed cost of a ticket".
If we use the cost of a ticket of 2 years ago ($6.58/ticket), then the income from the sale of 225 tickets this year would be ($6.58/ticket)(225 tickets), or $1480.50.