Answer:
2.66foot
Step-by-step explanation:
Given a tree which is 12 feet tall casts a 18 feet shadow.
We know that
[tex]Tanx=\frac{height of the object}{length of the shadow}[/tex]
This Tanx is same for the maialbox too so
[tex]\frac{height of the mailbox}{length of the shadow}=\frac{height of the tree}{length of the shadow}[/tex]
[tex]\frac{height}{4}= \frac{12}{18}[/tex]
height = 2.66 foot