So if you make them improper fractions the -2 1/2 would turn into -5/2 and the 3 1/2 would turn into 7/2. If you do a multiplicative inverse to the 7/2 that makes the equation
-5/2 x 2/7
-5 x 2= -10
2 x 7=14
So you would have -10/14
You can simplify -10/14 into -5/7 and that’s your answer