please help and explain how to solve

Answer:
A 45-foot tree will cast a 81-foot shadow.
Step-by-step explanation:
Set up a proportion.
I'll set mine up like this:
[tex]\frac{Height of Tree}{Shadow}=\frac{Height of Tree}{Shadow}[/tex]
Insert the values given then solve for the unknown (t).
[tex]\frac{25}{45}=\frac{t}{81}[/tex]
[tex](81)\frac{25}{45}=\frac{t}{81}(81)[/tex]
[tex]45=t[/tex]