1. The problem is to find the value of $x$ in a right triangle where one leg is 9, the other leg is $x$, and the hypotenuse is 12. 2. We use the Pythagorean theorem for right triangles: $$a^2 + b^2 = c^2$$ where $a$ and $b$ are legs and $c$ is the hypotenuse. 3. Substitute the known values: $$9^2 + x^2 = 12^2$$ 4. Calculate the squares: $$81 + x^2 = 144$$ 5. Isolate $x^2$: $$x^2 = 144 - 81$$ 6. Simplify: $$x^2 = 63$$ 7. Take the square root of both sides: $$x = \sqrt{63}$$ 8. Simplify the square root: $$x = \sqrt{9 \times 7} = \sqrt{9} \times \sqrt{7} = 3\sqrt{7}$$ 9. Approximate the value: $$x \approx 3 \times 2.6458 = 7.9374$$ 10. Since the options are 4.9, 5.4, 6.8, and 7.2, the closest value is 7.2. Final answer: $x = 7.2$ (Option D)