The shadow cats by the stick was 5 feet long while the actual stick is only 3 feet long which means the shadow makes it bigger by 2 feet. Take 2 feet away from 45 feet you will get 43 feet.
I hope you understand if you dlnt I will explain it more. Hope it helped too!
You do rise over run or y/x to find your answer. You go over 6 and up 10 to get from the lower point to the one on top. 10/6=1.666667 and rounded will be 1.7