1. **State the problem:** We have a right triangle KLM with a right angle at L. The side KL measures 3.1 units, LM measures $x$ units, and KM is the hypotenuse. 2. **Formula used:** In a right triangle, the Pythagorean theorem applies: $$ KM^2 = KL^2 + LM^2 $$ This means the square of the hypotenuse equals the sum of the squares of the other two sides. 3. **Apply the formula:** Let the hypotenuse KM be known or given. Since it is not provided, we assume it is given or we solve for $x$ if KM is known. If KM is known, say $KM = c$, then: $$ c^2 = (3.1)^2 + x^2 $$ 4. **Solve for $x$:** $$ x^2 = c^2 - (3.1)^2 $$ $$ x = \sqrt{c^2 - 3.1^2} $$ 5. **Example:** If the hypotenuse KM is given as 5 units (typical example), then: $$ x = \sqrt{5^2 - 3.1^2} = \sqrt{25 - 9.61} = \sqrt{15.39} \approx 3.9 $$ 6. **Conclusion:** Without the length of KM, $x$ cannot be found exactly. If KM is given, use the formula above to find $x$ and round to the nearest tenth. **Final answer (example with KM=5):** $$ x \approx 3.9 $$