Well this one can be solved with the Side-Angle-Side theorem.
Assuming the lamp post is at a 90 degree angle from the ground we have this:
Where B is the height of the lamp post, A is the length of the shadow, and b is the elevation of the sun casting the shadow.
The sum of the angles in a triange always add up to 180 degrees, so since we know two of the angles, the third is easy. 180 - 64 - 90 = 26 (Assuming the lamp post is angled 90 degrees relative to the ground.)
So far we have a=26 b=64 c=90 and A=8 B=? C=?
So the law of sines states that A/sin(a) = B/sin(b) = C/sin(c), therefore:
8/sin(26) = B/sin(64) = C/sin(90) = 18.25. (Fun fact: sin(90) = 1)
So solving for C: C/sin(90) = C/1 = C = 18.25
So now we have a=26 b=64 c=90 and A=8 B=? C=18.25
now to solve for B: B/sin(64) = 18.25 B=18.25*sin(64) = 16.4
Finally all the cards are on the table: a=26 b=64 c=90 and A=8 B=16.4 C=18.25
So to answer the question, the height of the lamp post is 16.4 feet.