my answer i got was -24/7 cant find the right answer !

It looks like your answer is upside-down.

7/8/(-3) is the same thing as 7/8 รท -3/1.

Now we have two fractions. To divide two fractions you flip the second one over so you change -3/1 into -1/3 and multiply.

7/8 x -1/3 = -7/24