You have two problems here. For the first one, a very good explanation can be found here on how to proceed
http://www.mathsisfun.com/algebra/trig-finding-side-right-triangle.html
You have the angle (82 degrees) and the adjacent side (4250 feet) but need the opposite side's measurement, so you are working with the tangent.
The second is classic Pythagorus: tree height is A (? feet), shadow cast (12 feet) is B, shadow tip to tree top is C (13 feet or the hypotenuse{H}).
Draw the picture, it will help makes things clearer.
So, A-squared plus B-squared equals C-squared:
A2 + B2 = C2
A2 + 122 = 132
A2 + 144 = 169
Move B to the right side of the equation
A2 = 169 - 144
Subtract B from C
A2 = 25
Take the square root of both sides of the equation
A = 5
The tree is 5 feet tall.