To find the rate at which Tabitha's coworker produces units, let's first analyze the given information:
- Tabitha works at a rate of \( \frac{1 \text{ unit}}{10 \text{ hours}} \), which means her rate is \( \frac{1}{10} \) units per hour.
- Together with her coworker, they produce 1 unit in 5.24 hours, giving them a combined rate of \( \frac{1}{5.24} \) units per hour.
Let \( x \) represent the rate (in units per hour) at which the coworker works. The combined rates of both Tabitha and her coworker can be expressed as:
\[ \frac{1}{10} + \frac{1}{x} = \frac{1}{5.24} \]
This equation correctly models the situation.
Now, let's look at the options provided. The valid rational equation is:
Start Fraction 1 over 10 End Fraction plus Start Fraction 1 over x End Fraction equals Start Fraction 1 over 5.24 End Fraction.
So the final answer is: Start Fraction 1 over 10 End Fraction plus Start Fraction 1 over x End Fraction equals Start Fraction 1 over 5.24 End Fraction.