Subtract Nick's distance from Posh's distance.<br><br>
&bull; Posh: 3 km = \(\frac{30}{10}\) km<br>
&bull; Difference: \(\frac{30}{10} - \frac{7}{10} = \frac{23}{10}\)<br>
&bull; Convert to a mixed number: \(\frac{23}{10} = 2\frac{3}{10}\)<br>
<br>
Final Answer: D: \(2\frac{3}{10}\) km