Is it true than an angle bisector creates two congruent vertical angles?

Yes, The bisector of an angle of triangle divides the opposite side in equal to each other

4,524 gallons

Step-by-step explanation:

The volume of any cylinder is 

 π (radius)² (height) .

The pool's radius is 1/2 its diameter = 8 ft.  So its volume is

 π (8 ft)² (3 ft)

= π · (64 ft²) · (3 ft)

= π · 192 ft³

= 603.2 ft³ .

(603 ft³) · (7.5 gal / 1 ft³) = 4,524 gallons

Hope this helps :D