Final answer:
The problem requires evaluating the expression (a - b) / (2a) given a = 3. Without a value for b, we cannot provide a definitive answer from the choices given. The expression simplifies to (3 - b) / 6 which requires b's value to find the numerical result.
Step-by-step explanation:
To find the value of (a - b) / (2a) when a is given as 3, we start by substituting the value of a into the expression. This gives us (3 - b) / (2 * 3). Simplifying this, we first multiply 2 * 3 to get 6, making our expression now (3 - b) / 6. Since we are looking for (a - b) / (2a), we can simplify further by subtracting b from 3. Assuming b is also equal to 3, substituting b = 3 into the expression would yield (3 - 3) / 6, which simplifies to 0 / 6, resulting in an answer of 0. However, since we are not given a specific value for b, we cannot determine the exact value of the expression without more information. The question might be under-specified if b is not defined. Without the value of b, we cannot select an answer from the given options.