Its simple!
First, you turn -3.9 into a fraction
-3.9=
Now u solve
(1) Convert mixed numbers into fractions (im sure you know how to do this)
(2) Multiply across on both the denominator and numerator (bottom and top rows)
(Remember, negative ×/÷ positive is always negative)
(3) Make ur answer into an even fraction
I hope this helped! Srry I'm not that good in english