Find c to form completing square

 (or 6.25)

Step-by-step explanation:

Let's do a simple square problem to see the relationship between the elements of the resulting equation...

As you see, the number of 'x' (6) is the double of the numeric part of the binomial expression (3), while the numeric-only part (9) is the square of the numeric part of the binomial expression (3).

So, if we look at the formula from the problem, we see the the number of 'x' is 5. To obtain the C value, we need to divide the 5 by 2... then get the square value of the result.

 (or 6.25)

step-by-step explanation:

12: 00 p.m. to 7: 00 p.m. is a total of 7 hours.

4: 00 p.m. to 7: 00 p.m. is a total of 3 hours.

this means that from 4: 00 p.m to 7: 00 p.m. this represents 3/7 of what was lost from 12: 00 p.m. to 7: 00 p.m.

after knowing this, after doing 11,600 - 6,800 = 4,800

4,800 represents 3/7 of what was lost for 7 hours.

we then divide 4,800 by 3 which gets 1,600.

because we know that 1,600 represents 1/7 of how much water was lost, we just have to multiply by 7, which gets 11,200.   after adding 11,200 to how much water was left at 7: 00 p.m. which was 6,800. 11,200 + 6,800 = 18,000

this means that the pool originally had 18,000 gallons in the pool.

you can also check your work by doing 18,000 - 4(1600), which becomes           1800 - 6400 which gets you 11,600.

thats not a system of equations, that is a solution