A new threat to Bulgaria's stability is the week-old miners' strike for a trebling of minimum pay.为期一周的矿工罢工要求最低工资增加两倍，这对保加利亚的社会安定构成新的威胁。They will have to pay much more when rents treble in January.一月份房租增加两倍时，他们将被迫多付不少钱。We expect to triple our profits next year.我们期望明年利润增加两倍。He has trebled his income during the last few years.在过去几年中他的收入已增加两倍。