We are asked to find the value of $f$ in the equation $3 = 2f + 15$.

1. Problem Description

We are asked to find the value of $f$ in the equation $3 = 2f + 15$.

2. Solution Steps

To solve for $f$, we need to isolate it on one side of the equation.

First, subtract 15 from both sides of the equation:

$3 - 15 = 2f + 15 - 15$

$-12 = 2f$

Now, divide both sides of the equation by 2:

$\frac{-12}{2} = \frac{2f}{2}$

$-6 = f$

Therefore, $f = -6$.

3. Final Answer

$f = -6$