Reena walks $6\text{km}$ to the North, then turns East and walks $8\text{km}$. What is the straight-line distance from her starting point?

To find the straight-line distance from the starting point, we can model Reena's path as a right-angled triangle where:
* The vertical side (North movement) is $a=6\text{km}$
* The horizontal side (East movement) is $b=8\text{km}$

Using the Pythagoras theorem, the straight-line distance ($c$) is the hypotenuse:

$$c=\sqrt{a^2+b^2}$$

$$c=\sqrt{6^2+8^2}$$

$$c=\sqrt{36+64}$$

$$c=\sqrt{100}=10\text{km}$$

Therefore, the straight-line distance from her starting point is $10\text{km}$.