The solution to the ditloid "5 B on a C" is "5 Balls on a Pool Table." Ditloids are a form of word puzzle where numbers and letters represent words or phrases. In this case, "B" stands for "Balls" and "C" represents "Table."
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You add the two distances together, so the solution is 10m + 5 m = 15m.
1973: Britain Enters the Common Market.