Answer:
The tree is 28 ft
Explanation:
We can solve this problem by using proportions. Take the size of the item over the shadow.
40 ft pole x ft tree
-----------------------= -----------
12 ft shadow 8.4 ft shadow
Using cross products
40 * 8.4 = 12 * x
336 = 12x
Divide each side by 12
336/12 = 12x/12
28 ft = x