I would suggest converting to fractions. -5.2 is equal to -52/10, and 3.9 is equal to 39/10. To divide -52/10 by 39/10, multiply -52/10 by the reciprocal of 39/10 (which is 10/39).
So you would set this up like:
-52 10
----- x ----- =
10 39
cancel out the 10s. just divide-52 by 39, and you have your answer.
or divide 52 by 39, just know that the answer will be negative.
52/39=1.33, or 4/3, or 1 1/3.
