1. **State the problem:** We need to find the length of the midsegment $RT$ in trapezoid $ZRWX$ where $ZR$ and $WX$ are the parallel sides. 2. **Recall the midsegment formula for trapezoids:** The length of the midsegment connecting the midpoints of the legs is the average of the lengths of the two parallel sides. $$ RT = \frac{ZR + WX}{2} $$ 3. **Identify the given lengths:** - $ZR = 13$ - $WX = 7$ 4. **Calculate the midsegment length:** $$ RT = \frac{13 + 7}{2} = \frac{20}{2} = 10 $$ 5. **Conclusion:** The length of the midsegment $RT$ is 10 units.