Part A: A number is increased by 54. The sum is then divided by 9. The result is 21. Write an equation to represent the description above. Use n for the number.

Equation:

Part B: Find the value of n. Show your work.

n =

Part C: Choose two numbers and use them to do the following:
Write an equation that shows your first number added to n equal to your second number. Solve your equation for n.

Equation:
Solution:​

(n +54)/9 = 21; 135= n

Step-by-step explanation:

(n+54)/9 = 21

n+54/9 *9= 21*9

n+54-54 = 189-54

n= 135

the first part is simply recognizing the order its written and the words used.

So to start off with, they use the turn "a number" so we know there's going to be some form of a variable. From there it says "increased by" rather than "multiplied" or "doubled" or something of that nature, so we know its adding 54 rather than multiplying. Then, the next part says that "the sum" which is another key term for addition, "is then divided by 9". So we can assume so far that a variable plus 54 is added together to get a number, which is then going to be taken and divided by 9. The last part says "the result is 21", which simply means that we need to end up with 21.

So once we gather all this information, we can put it together as so: (n +54)/ 9 = 21.

I put parentheses around the n + 54 to make sure that the equation is following the system of equations (PEMDAS).

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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.