How can I write a division sentence of 6 3/4

You can write any division sentence like 63 divide by 3, 63÷3,

the mistake in the pattern is that :

b. the decimal point was moved one too many place values each time

the correct pattern could be made by :

b. moving the decimal point to the right the same numbers of place values as the exponents

so, converting firstly the mixed fractions to improper fractions and then "adding".