1. **State the problem:** Murphy's golf score changed from 2 over par to 3 under par. We want to find the total change in his score relative to par. 2. **Understand the terms:** "2 over par" means Murphy's score was $+2$ relative to par. "3 under par" means Murphy's score was $-3$ relative to par. 3. **Calculate the change:** The change in score is the final score minus the initial score. $$\text{Change} = (-3) - (+2) = -3 - 2 = -5$$ 4. **Interpretation:** A change of $-5$ means Murphy improved his score by 5 strokes relative to par. **Final answer:** Murphy's score improved by 5 strokes.