How many seven-digit numbers are there when 0 , 7 , and 2 cannot be the leading number?

 9,000,000
-2,000,000 (1,000,000 for each of the numbers taken out except 0, a number    7,000,000                   can't start with 0 unless it is 0 or a decimal.)

If is congruent to,then m is the midpoint