请问这题怎么解?

sydneyang

"怎么算的还是没有理解"

Let a three digit number be xyz. Statement 1 says z+9=x3z. So y (tens digit) must be a 2, because z cannot be zero; Z must be greater than 1. Any number added by 9 increases the tens digit by 1, so it becomes 3.

Am i making sense?