well ,the proof is high school level and it is the following:How does this "prove" whether the y in the OP's question is in the numerator or denominator?

=...........................................by using the definition of division:

==..................................................by using the theorem : and the axiom : 1a =a

==...................................................by using the axiom : (ab)c =a(bc)

==..................................................by using the theorem in Natural Nos 48 =24.2

==....................................................by using again the axiom : (ab)c = a(bc)

==............................................................................by using the axiom : and also the axiom :1a = a

=................................................................................by using again the definition of division