SOLUTION: a girl sout 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

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Question 173429: a girl sout 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?
Answer by Mathtut(3670) About Me  (Show Source):
You can put this solution on YOUR website!
lets call the number of cookies sold in week 1,2 and 3: a,b,and c respectively
:
b=a+5.......eq 1---->a=b-5 revised eq 1
c=2b........eq 2
a+b+c=431...eq 3
:
lets take the value of a from revised eq 1 and the value of c in eq 2 and plug them into eq 3
:
(b-5)+b+(2b)=431
:
4b-5=431....combining b terms
:
4b=436.....combining constants
:
highlight%28b=109%29..........................boxes of cookies sold 2nd week
:
using revised eq 1 highlight%28a=b-5=109-5=104%29boxes of cookies sold week 1
:
using eq 2highlight%28c=2b=2%28109%29=218%29.........boxes of cookies sold week 3