having problems getting this equation into nand gates only... I'll type the gates because I don't have any program where I could get the symbols...
(a1 xnor b1) and (a2 xnor b2) and (a3 xnor b3) and (a4 xnor b4)

 

That instructor of yours really likes NAND gates, don't they? Adimittedly, enough NAND gates can indeed perform any logic function, but I disagree with the notion of their economy.

Anywhoo, here's a hint from the 'ol Boolean Bag O Tricks:

A XNOR B = (A NAND (A NAND B)) NAND (B NAND (A NAND B))

 

not sure I understand your advice. Looks like one xnor gates turns into 5 nand gates? we have limited supply of gates in our schools laboratory so thats why we have to use nand gates...

 

First convert, then simplify.