Let h represent the height of the building. Then the difference between the two angle measurement locations is
.. h/tan(39°) -h/tan(50°) = 300 ft
.. h = (300 ft)/(1/tan(39°) -1/tan(50°))
.. h ≈ 758 ft
The height of the building is about 758 feet.
"Classify the polynomial by the number of terms" means a term contains both the variables and its coefficient. For example a "monomial" has one term like
.
A binomial has 2 terms like 
A trinomial has 3 terms like 
And a polynomial has 4 or more terms.
So basically one can classify the type of polynomial by counting the number of terms in a given equation.