Question

How would I find the height of the clocktower using this information?

Bobby, who is 5’6” tall, took a square of paper, folded it in half and then taped a straw to the hypotenuse. Then holding the bottom of the paper level, he walked back from the clocktower until he could sight the top of the clocktower through the straw. At that point he was 42 feet from the clocktower. He also noted his shadow was 8 ft long. 2 hrs later, he came back and measured the clocktower’s shadow and it was 20 ft long.

Answer 1

What is your question?

Answer 2

My question is:
"How would I find the height of the clocktower using this information?" as well as "What is the height of the clocktower?

Answer 3

Confusing wording.

Since you are sighting through the straw, the straw forms the hypotenuse.
You can sketch 2 similar triangles and form ratios
Bobby's height / length of Bobby's shadow = height of tower/tower shadow
5.5/8 = h/(42+8)
8h = 5.5(50)
h = 34.375

The fact that "2 hrs later, he came back and measured the clocktower’s shadow and it was 20 ft long." has nothing to do with it.