Answer:
21x²
Step-by-step explanation:
hopefully A is a typo
Answer: A (if it's just a typo) or [tex]21x^{2}[/tex]
Since it's the same variable and same exponent, you just need to add the whole numbers and put the same variable and exponent.
12 + 9 = 21
[tex]21x^{2}[/tex]
