Answer:
A. 1.7 ft
B. 5.8 ft
Step-by-step explanation:
Part A.
The seesaw forms a triangle as follows
So, we can relate the angle of 25°, the side of 4 ft, and the height of the central support h with the trigonometric ratio sine as follows

Solving for h, we get

Therefore, the height of the central support is 1.7 ft
Part B.
For this part, we have the following diagram
Therefore, there is another triangle formed with hypotenuse d, an angle of 80°, and a side of 1.7ft. Using the trigonometric ratio cosine, we get

Solving for d, we get

Then, we want to know the value of x, so we can calculate x as follows
x = 9.8 ft - 4 ft = 5.8 ft
So, the answer for part B is 5.8 ft