Elgamal attack example with ciphertexts
The exercise is not about ElGamal in the slightest. I would even call it bogus:


"$n$" would be the modulus, which is clearly not prime, being divisible by $2$.
The values $pk,g,n$ seem to be in decimal, the values $c_1,c_2$ in hexadecimal - but nowhere stated what kind of encoding is used.
It looks like exponentiation in the integers was used, but $c_1$ isn't a power of $g$
Trying around in WolframAlpha how those values were generated I got nothing, but $c_1$ isn't divisible by $n,pk$ or $g$ when considering them as decimal or hexadecimal encoding.
Is it a coincidence, that if you want to do some WolframAlpha computations with these numbers in decimal, the input field is just not long enough? $c_1$ alone fits, but it leaves you just with 5 more input characters. Using all numbers in hex works, tho.


Since the source you quoted is another question how to interpret this, this is definitely not the author.

At this point I can only suggest looking for reliable sources, e.g. exercise material from universities, textbooks or examples on Wikipedia. Looking at any kind of material where you don't know the author and the background has the potential to actually damage your learning progress.