Answer:
C. -24
Explanation:
Hello!
To solve this we have to follow the order of PEMDAS
Parenthesis, exponents, multiplication and division, addition and subtraction

Parenthesis first

Exponents next
21 + 36 - 27 * 3
Multiplication and division from left to right
21 + 36 - 81
Addition and subtraction from left to right
57 - 81 = -24
The answer is C.-24
Hope this helps!