1. Replace the x in the equation with 2. f(2) = 3(2)*2-x(2)
2. Simplify, multiply 3 by the 2 in parenthesis, then by the 2 next to it (this will give you 12 because 3*2*2 = 12) Then multiply the x with the 2 in the parentheses next to it. f(2) = 12-2x
This is the most you can simplify so your answer could probably be 12-2x.
When you say 3x2, I think you mean 3x^2. But I am not sure. So, we know that f(x)=3x^2-(2)3. And we have to find what f(2) is. So, we simply plug in the 2 in the equation.
