1. **State the problem:** We have a right triangle with hypotenuse length 11 units and one leg length 5 units. We need to find the length of the other leg. 2. **Formula used:** In a right triangle, the Pythagorean theorem applies: $$a^2 + b^2 = c^2$$ where $c$ is the hypotenuse, and $a$, $b$ are the legs. 3. **Apply the formula:** Let the unknown leg be $x$. Then: $$5^2 + x^2 = 11^2$$ 4. **Calculate squares:** $$25 + x^2 = 121$$ 5. **Isolate $x^2$:** $$x^2 = 121 - 25$$ $$x^2 = 96$$ 6. **Find $x$ by taking the square root:** $$x = \sqrt{96}$$ 7. **Simplify the square root:** $$\sqrt{96} = \sqrt{16 \times 6} = \sqrt{16} \times \sqrt{6} = 4\sqrt{6}$$ 8. **Final answer:** The length of the third side is $4\sqrt{6}$ units. **Answer choice:** B. 4√6 units