In the ratio 3:4=6:8, if 6 is added to the last term of the first ratio, how much should be added to the last term of the second ratio to make the ratio valid?
比例3：4=6：8中，如果第一个比的后项加上6，那么第二个比的后项应该加上多少，才能使比例成立？
<result>12</result>