This is actually quite trivial, and almost the prototype on a typical M&B question. Just wondering why you struggle with this?
Anyhow:
Always set it up like this:
DOM
TL
ZFM (=TL+DOM)
Fuel
TOM (=ZFM + Fuel)
TripFuel
LM (= TOM - TripFuel)
DOM : 48.000
TL : (maxzfm - DOM) 22.200
(max) ZFM : 70.200
Fuel 9.800
Takeoff mass (ZFM + fuel) = 80.000. (overload 1.800)
Trip fuel 7.000
Landing mass (Takoff mass - trip fuel) = 73.000 (Overload 5.000)
So max Traffic load must be 22.200 - 5.000 = 17.200.
Man takeoffmass = 80.000 - 5.000 = 75.000