and the amount of the surgery also expensive of living other country for one month by the way the ticket is 5400$ you need to multiply it by two (home and away)
I also don't understand where your numbers are coming from. What exactly is 10800?
Why not give out all the details beforehand? Return flights are of-course cheaper than two one-ways but this is what we would have evaluated:
PRICE_PASSPORT = 600
PRICE_TICKET = 1200
INSTANCES = 3
3 * 1200 * 2 = 7200 (COST OF FLIGHTS)
3 * 600 = 1800 (COST OF PASSPORTS)
18000 - 9000 = 9000 (COST OF SURGERY)
What, exactly, would be the details that we're missing?