The answer is A hope this helps!
It will take 13.33 days to fill it to 6,000 gallons.
6^5 = 6•6•6•6•6
x^7 = x•x•x•x•x•x•x
x^5 = x•x•x•x•x
5^6 = 5•5•5•5•5•5
This is the Pythagorean theorem where the 2 legs of a triangle squared add up to equal the squared hypotenuse (a^2 + b^2 = c^2)
The equation would be
12^2 + 5^2 = x^2
144 + 25 = 169
The square root of 169 = 13
Answer - 13 ft