If the two sides balance, all eight coins on the scale are real, and the fake must be among the remaining four.

如果双方平衡， 天平上的八个硬币都是真的，剩下的四个硬币中一定是假的。

Similarly, if the two sides balanced after your substitution, then one of the three plus coins you removed must be the heavier one.

同样，如果你替换后两侧平衡，那么你移走的三个加号硬币中的一个一定是较重的那个。