5/4 divided by 1/3 First you flip the second fraction. so its now 5/4 divided by 3/1 then you cross multiply so 5 times 3 = 15 and 4 times 1 = 4 which means the fraction is 15/4 (or 3 3/4 in simplest form)
It works because 7 x 9 x 10 is the same thing as 7 x 90, since 9 x 10 is just 90. So basically he is just writing more but the answer will still be the same.
