1. **State the problem:** We have a population with mean $\mu = 37$ and standard deviation $s = 6$. It is standardized to a new distribution with mean $\mu = 50$ and standard deviation $s = 10$. An individual has a score $X = 55$ in the new distribution. We want to find this individual's original score in the original distribution. 2. **Formula used:** The z-score formula is: $$z = \frac{X - \mu}{s}$$ where $X$ is the score, $\mu$ is the mean, and $s$ is the standard deviation. 3. **Step 1: Find the z-score of the individual in the new distribution.** $$z = \frac{55 - 50}{10} = \frac{5}{10} = 0.5$$ 4. **Step 2: Use the z-score to find the original score in the original distribution.** Rearranging the formula: $$X = z \times s + \mu$$ Substitute $z = 0.5$, $s = 6$, and $\mu = 37$: $$X = 0.5 \times 6 + 37 = 3 + 37 = 40$$ 5. **Answer:** The individual's original score was $\boxed{40}$. This corresponds to option a. X = 40.