To find a, we can use Pythagoras theorem, where:
a^2+b^2 = c^2
a and b is the width and length, while c is the longest side.
In this case:
30^2+a^2 = 34^2
Put the numbers without unknown on one side:
a^2 = 34^2 - 30^2
a^2 = 256
a = _/256
a = 16
Therefore, a = 16km.
Hope it helps!
