The difference 942 – 249 is a positive multiple of 7. If a, b, and c are nonzero digits, how many 3-digit numbers abc are possible such that the difference abc

The difference 942 – 249 is a positive multiple of 7. If a, b, and c are nonzero digits, how many 3-digit numbers abc are possible such that the difference abc – cba is a positive multiple of 7 ?

A、142
B、71
C、99
D、20
E、18

答案：E

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