To get -3.2 into a fraction, we will multiply the number by
to get:


-3.2 = -17/5
To get -1 7/8 into the fraction form of
, we will multiply the 1 by the denominator 8 to get 8, which we will add to the numerator of 7 to get a final fraction of -15/8. This is represented as:

-5/6 is already in the form a/b.
To get 3 4/5 into the fraction form a/b, we will do the same process as the first mixed fraction. First, multiply the whole number by the denominator to get 15, which we will then add to the numerator of 4 to get the fraction 19/5. This is represented as:

To summarize, our four numbers are now -17/5, -15/8, -5/6, and 19/5. -17/5 is the smallest, because its numerator is over 3 times the value of the denominator, but it is negative. -15/8 is the next smallest, because its numerator is around 2 times the size of the denominator, but it is negative. -5/6 is the next smallest, because it is negative and its numerator is less than its denominator. 19/5 is the biggest because its numerator is almost 4 times the value of the denominator.
Thus, the order (greatest to least) would be 19/5, -5/6, -15/8, -17/5, or 3 4/5, -5/6, -1 7/8, -3.2.