Is it improper to have a fraction with a decimal in it

Like -5.5/3? Should I change it to -11/6? (this is for slope)

Yes it is improper. Since a decimal is a fraction, -5.5/3 is really just a fraction over a fraction. So yes you should change it.

Negative five and a half divided by three?

Yeah, it's wrong, but sometimes, if it makes it easier for you to see something it's ok to work with as long as you put it back either as a decimal of fraction when you turn it in..

a fraction is just another way of writing a fraction. so, for example:
1.5/2 is the same thing as 3/4 (1.5/2 = 3/2 /2 = 3/4)
so you shouldn't mix them .if you r working with fractions everything needs to be fraction

A decimal is just another way to express a fraction, so you should not have a decimal in the fraction.

Yes, they both have the same answer. Just remember to multiply both numerator and denominator with the same number like -16.5/9 and -22/12

Yes because you cant leave it like that it would be very hard and difficult so yes change it

Yes you should not mix the two.