equation

                                      (8/125)*___ = 5/2  

                                         8          x          5  

                                      ––––  •  –––  =  –––  

                                       125        1          2  

divide both sides by 8 / 125  

                                                             5           8  

                                                    x  =  –––  ÷  ––––   

                                                             2         125  

to divide by a fraction invert and multiply  

                                                             5         125  

                                                    x  =  –––  •  ––––   

                                                             2           8    

                                                               5         125          625  

                                                    x   =   –––  •  ––––   =   –––––   

                                                               2           8             16  

.

This is not an algebraic response 

Notice that 8 is 2³ and 125 is 5³

So, the blank should have 5⁴/2⁴ which will be 5000/2000 which is equal to 5/2

Hope this helps :D