Write the expression for $f(5)$ by plugging in $5$ for $x$ in $4x-6$. What do you get?

First do the multiplication with $4$ and $5$, then apply the $-6$. Be careful with the order of operations.

In Desmos, type f(x)=4x-6 to define the function.

On a new line, type f(5) and look at the numerical output that Desmos gives; that value is the answer to the question.

The function is defined as $f(x)=4x-6$. The notation $f(5)$ means "take the expression for $f(x)$ and replace $x$ with $5$."

Start with $f(x)=4x-6$ and plug in $x=5$:

First multiply $4(5)$:

Now subtract $6$:

So the value of $f(5)$ is $14$.