Hey there!
GUIDE:
MONOMIAL has ONE TERM
BINOMIAL has TWO TERMS
TRINOMIAL has THREE TERMS
POLYNOMIAL has MANY TERMS
Now that we got that information we already found out what your answer should be.
The number 12 is a MONOMIAL because it has ONE term. So therefore, to answer your question. YES 12 is a monomial ☑️
Good luck on your assignment and enjoy your day!
~LoveYourselfFirst:)