How high is a tree that cast a 27 -ft shadow at the same time a 6-ft pole cards a shadow which is 4-ft long

In this question, you must identify the scale factor, make a proportion and solve for the missing value.

So, to find the scale factor, look at your numbers given. (Drawing a picture like the one shown may help you keep it straight)
Ask yourself: What did we do to 27 to get four?
The answer to this question can be solved by dividing 27 by 4.
This leaves you with:
6.75

So, since you know this scale factor relationship, you can apply it to the height of the pole, which is 6.
Multiply the height of the pole, 6, by the scale factor, 6.75, to get the height of the tree.
This leaves you with:
40.5

So the final height of the tree is 40.5 feet.