To divide one fraction by another you have to turn the second one "upside down", this means, that you have to use the reciprocal fraction.
Two fractions are reciprocal when their multiplication is equal to 1, for this example:
4/5 * 5/4= 1 this means that 5/4 is reciprocal to 4/5
Once you have the reciprocal fraction, insead of doing a division you have to multiply them:
-7/10 * 5/4
Now you have to multiply "numerator * numerator" and "denominator * denominator"
-7 * 5= -35
10*4= 40
-35/40 = -7/8