If you want to get the unknown number, you should know the knownnumber first.
如果要想求出未知数，你首先得知道已知数。
2
A knownnumber rectangular area is a Y square centimetre, one side is long for X is that this rectangular circumference is several centimetres centimetre.
已知一个长方形的面积为Y平方厘米，一边长为X厘米，则这个长方形的周长为几厘米。
3
By report, US na German is a knownnumber of in the world only's develop this strange disease clan, but the whole world "nothing fingerprint people" final total does not exceed 20!