Difficult to explain without a drawing but you can draw one out yourself.
Work out the change of CG from BEM to TOM.
BEM Mass 1200kg x arm 3.0m = 3600kgm
Pilot and pax in front seats: mass 160kg x arm 2.5m = moment 400kgm
Fuel 100kg x arm 3.0m = moment 300kgm
Add masses and moments to find:
TOM = 1460kg TOM moment = 4300kgm
TOM CG = moment/mass = 4300/1460=2.95m
The BEM CG was at 25% MAC with an arm from the datum to 25% MAC of 3m. The MAC is 2m which means the CG is 0.5m from LEMAC
Now the TOM CG is 2.95m which means it is 0.45m from LEMAC
As a % MAC then : 0.45/2 x 100 = 22.5%