ANSWER and EXPLANATION
We are given the division:
6499 ÷ 7
a. That is, how many 7s can we find in 6499 and what would be the remainder after finding all the possible 7s.
The division is therefore:
6499 ÷ 7 = 928 R 3
b. Jim said there is a remainder of 7.
This is not possible, because the divisor is 7.
So, if the remainder is 7, then we would have:
7 ÷ 7 = 1
So, the mistake Jim made is assuming that 7 can be a remainder of the division.