Answer:
b = 12 Km
Explanation:
using Pythagoras' identity in the right triangle
the square on the hypotenuse is equal to the sum of the squares on the other 2 sides , that is
b² + 16² = 20²
b² + 256 = 400 ( subtract 256 from both sides )
b² = 144 ( take square root of both sides )
b =
= 12