The answer to your question would be shown in steps. The decimal form is -1.2. You need to do a formula called "Keep, Change, Switch," which -3/4 is kept, division is turned into multiplication, and 5/8 is switched to make 8/5. Now we do the math, so we multiply -3 by 8 and 4 by 5, giving us from a fraction, -24/20, but you can simplify that, giving us the fraction, -1' 1/5 (I put ' as in that any number to the left of ' is a whole number, not a fraction for a numerator or denominator.
Hope this helped!
Nate