Answer:
so let's call the unknown number x.
-5/4 x X = 7/2
by changing the subject, X = 7/2 / -5/4
to divide fractions, we turn the fraction we're dividing by upside down and change the sign to multiplication. so X = 7/2 x 4/-5
after multiplying, X =>28/-10
simplified, X = 14/-5