6. When an 8-foot tall fence casts a 5 -foot shadow, a tree next to it casts a 20 -foot shadow. Find the height of the tree.

Step 1 ：\(\frac{h_{tree}}{20} = \frac{8}{5}\)

Step 2 ：\(h_{tree} = \frac{20\times 8}{5}\)

Step 3 ：\(h_{tree} = 32\)