Your answer for -0.75 is -3/4. Here is how I got the answer. Just to show the work.
-0.75/1 x 100/100= -75/100
Greatest common factor is 25, so divide the numerator and denominator by this.
So, -75/2=-3
Combine the numbers to form a fraction.
-3/4
Hope this helps you. Good luck.
~Karleif