The function f is defined for each positive three-digit integer n by f(n)=
| x | y | z |
| 2 | 3 | 5 |
where x,y and z are hundreds,tens,and units digit of , respectively. If m and v are three digit positive intergers such that f(m)=9f(v), then m - v=?
8
9
18
20
80
请教解题过程.
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