How do you evaluate the function \[f(x)=6x\] when x=3?

Hint: In the above question we have to find the value of the given function at a point. Thus, we will substitute the value of the point in the definition of the given function. In this question the given function is simplified. So, by simply substituting the point we can get the answer.

Complete step-by-step solution:
The question belongs to the concept of function notation. A function is a binary relation between two sets that associates every element of the first set to exactly one element of the second set. The way a function is represented is called as function notation. We have four ways to represent a function. A function can be represented graphically, mathematically, verbally and algebraically. Here we will follow the function rule. A function rule is how to convert an input value into an output value.
So, the given function is \[f(x)=6x\] . As we have to find the value of the given function at x=3.
Therefore, we will substitute the value of x in the definition of the given function.
\[\begin{align}
  & f(x)=6x \\
 & \Rightarrow f(x)=6(3) \\
 & \Rightarrow f(x)=18 \\
\end{align}\]
Therefore, the value of the function at x=3 is 18.

Note: While solving the above question do check whether the given function is in simplified form or is in terms of the other function. Solve the question step by step, do not skip or jump directly to the solution. Keep in mind the procedure for solving these type of questions.