Answer
6
2
48
8
7
Work Step by Step
In the British compound a ration of cheese can be exchanged for 6 cigarettes. At 2 cigarettes each , those 6 cigarettes can be exchanged for 2 coffee rations. In the French compound those 2 coffee rations are worth 48 cigarettes, which can be exchanged in the British compound for 8 cheese rations ($48\div6$).
Through trade, the British prisoner has turned 1 cheese ration into 8, for a net gain of 7 cheese rations.
