Total mass 2900 kg
Centre of gravity (cg) location station: 115
Aft cg limit station: 116
The maximum mass that can be added at station 130 is:

La ecuación a resolver seria:

MaxCG = 116 = (2900·115 + m·130)/(2900+m)

Aislando m queda:

m=207,14 kg

O de forma facil:

desplazamiento CG=masa añadida*(estacion-CG)/(masa añadida+masa original avion)

1=m*(130-115)/(2900+m)
2900+m=15m
2900=14m
m=2900/14=207 kg

Saludos