Question

A girl scout troop sold cookies. If the girls sold 5 more boxes the second week than they did the first, and if they doubled the sales of the second week for the third week to sell a total of 431 boxes of cookies, how many did they sell each week?
They sold _____ boxes the first week, _____ boxes the second week, and ____ boxes the third week.

Answer 1

Answer:

IT'S CORRECT!

Step-by-step explanation:

Answer 2

So,

We have three placeholders.

x, y, and z will represent the number of cookie boxes they sold for the first, second, and third weeks, respectively.

"The girls sold 5 more boxes the second week than they did the first."
x + 5 = y

"They doubled the sales of the second week for the third week."
z = 2y

"To sell a total of 431 boxes of cookies"
x + y + z = 431

Now we have our three equations.
x + 5 = y
z = 2y
x + y + z = 431

Obviously, we can substitute y and z in the last equation, because the other two open sentences tell us what they are.
x + (x + 5) + 2(x + 5) = 431
x + x + 5 + 2(x + 5) = 431

Collect Like Terms.
2x + 5 + 2(x + 5) = 431

Distribute.
2x + 5 + 2x + 10 = 431

Collect Like Terms.
4x + 15 = 431

Subtract 15 from both sides.
4x = 416

Divide both sides by 4.
x = 104

Now we can use the other two original sentences to figure out what y and z are.
x + 5 = y
104 + 5 = y
109 = y

z = 2y
z = 2(109)
z = 218

Now, to check, add x, y, and z.
x + y + z = 431
104 + 109 + 218 = 431
213 + 218 = 431
431 = 431 This checks.

The Girl Scouts sold 104 cookie boxes on the first week, 109 boxes on the second week, and 218 boxes on the third week.