Hello!
You can use the Pythagorean Theorem to solve this
![a^(2) + b^(2) = c^(2)](https://img.qammunity.org/2019/formulas/mathematics/college/3byu32yniwf4k67ty0w3p5iut2e0wsjpqf.png)
c is the hypotenuse
a and b are the legs
Put in the values you know
![1.5^(2) + b^(2) = 1.7^(2)](https://img.qammunity.org/2019/formulas/mathematics/college/wogqyxckpzckrntku3o0l1thuqsazyz16w.png)
Square the numbers
![2.25+ b^(2) =2.89](https://img.qammunity.org/2019/formulas/mathematics/college/pcr63xzze7ocooxodyq4dbuz2sulkkpjeo.png)
Subtract 2.25 from both sides
![b^(2) =0.64](https://img.qammunity.org/2019/formulas/mathematics/college/l2vklenhr6ylkvwtb73buzue2x54vzrnlg.png)
Take the square root of both sides
b = 0.8
The answer is 0.8km
Hope this helps!