What exactly does a 10-transistor XOR gate look like?
Homework?

What are they trying to teach you?

Look at the various versions and see how they work.
Going from eg 12 to 8 they replace 4 with passives in some manner.
Why did they replace 4?
Could they have just replaced 2?
Could any 2 of 4 have been been replaced
... or just 2
........or 'this 2' or 'that two' but not just any 2 ...?   

These are probably exactly the questions that you are meant to be asking yourself and why the question exists.  

Try not to just look for finished "answers".
Rather, try to see why the answer is possible and what it teaches you.

IMPORTANT:  The above is a MUCH BETTER answer than the one you asked for.
If you do what it suggests you will learn something AND (probably) be pleased when you do so.
If you do not try to answer this sort of question yourself and just go looking for "pictures" that you do not understand then you will fail - maybe the course but more importantly, you will be less successful than you could be.