How do you divide fractions with different denominators with whole numbers?

First off, you make the mixed fraction with only 1 numerator and one denominator, a mixed fraction will end up with a numerator bigger than the numerator, because, it has several whole, in the case of 7 3/4, it has 7 wholes, anyhow, a fraction with a bigger numerator than denominator is so-called an "improper fraction". 

anyhow... you'd multiply the whole times the denominator, and add the numerator, and that's the new numerator

let us divide those