You always want to divide the top number by the bottom, so it is -24/7. If you divide that, you get a very long decimal. So the easiest way to do this is to make a mixed number.
7 goes into 24 3 times. that means 3 is the whole number. 7 times 3 is 21, so you subtract 24-21 and you get 3. The denominator always stays the same, so you are left with 3/7.
the mixed number would be 3 3/7.
But the negative is still there from the beginning, meaning it would be -3 3/7.