Which is most likely to be the first step in solving a system of linear equations by substitution

Astick 2 m long is placed vertically at point b. the top of the stick is in line with the top of a tree as seen from point a, which is 3 m from the stick and 30 m from the tree. how tall is the tree?

How to simply and write the answer n a whole number

Hello, i need compare km^2 and km. what's difference in this?