ElectricPavlov

He starts at 8000 gallons      when he adds 2000 gals it will overflow

120 gal go out each hour       225 gal goes in each hour     net : 105 gal per hour IN

105 x = 2000 gal

x = 19.048 hours until overflow      

1 pm + 19 .048 hours =  8.048 AM  = ~~8 :03 AM   Since he checks every hour, he will first see the overflow at   9:00 AM

I think you left off some numbers   such as

9998    9992    9982   9928    etc   

5 choices for first digit

    5 choices for 2nd digit

         5 choices for 3rd digit

              5 choices for   4th digit       5 x 5 x 5 x 5 = 5⁴ = 625 numbers

Sorry ....I keep misreading Q's      625 possible numbers    the ones that end in  2 or 8   are even  so, I think 2/5 x 625 = 250 EVEN numbers

The 'x' value of the vertex of the graph of this bowl shaped parabola  will be given by    - b / 2a    where   b = 9   a = -2

   use this value of 'x' in the equation to find the 'y' coordinate of the vertex.....

Jack - 1 = Jill +1      (given)    or   Jack = Jill +2     (sub into the next equation)

Jack +1 = 2 (Jill-1)       (given)

Jill +2    +1   = 2 Jill - 2

Jill = 5          Then    Jack =7

Yeppers !   c = 3

10 c 3 =   10!/(7!3!) = 120 ways

it is an odd number   because dividing by 2   leaves 1

  it is a multiple of 3   + 2

and an even multiple of 7            7   14   21   28   35    42    49    56    63    70   77    84   91   98    105    112    119   126   133   140  147  

     so for the above rules I have written so far     35   77   119      fit the bill so far

                      divide by 4 to find which leaves 3 remainder :   119

Factor 

(x^2-4x+3)(x+5) - (x^2+4x-5)(x-c)= 0

(x-3)(x-1) (x+5)           - (x +5)(x-1)(x-c) = 0     divide out  (x+5)  and  (x-1)

(x-3)                  -   (x-c )  = 0         think you can take it from here?

I count NINE ways.... you ?       (edited)