Question 288392
A quadratic function is given below:
f(x)=3x^2-x+6
What is f(2)?
A. 40
B. 28
C. 16
D. 4 
.
f(x)=3x^2-x+6
f(x) is a "function of x" -- meaning for a particular value of x you can find the value of f(x).
In your case, when they say "what is f(2)"?  They are asking you what the value of f(x) when x=2.  So, simply plug in the value of 2 for x and solve:
f(x)=3x^2-x+6
f(2)=3(2^2)-2+6
f(2)=3(4)-2+6
f(2)=12-2+6
f(2)=10+6
f(2)=16