SOLUTION: At the Cafe, a lunch of iced tea, a veggie burger, and fries costs $7.56, with the fries costing twice as much as the iced tea. Next week at the Cafe, the price of the iced tea wil

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: At the Cafe, a lunch of iced tea, a veggie burger, and fries costs $7.56, with the fries costing twice as much as the iced tea. Next week at the Cafe, the price of the iced tea wil      Log On


   



Question 1038941: At the Cafe, a lunch of iced tea, a veggie burger, and fries costs $7.56, with the fries costing twice as much as the iced tea. Next week at the Cafe, the price of the iced tea will increase 10% and the price of the veggie burger will increase 25%. After the increase, the same lunch purchase will cost $8.68. Find the price of each item before the increase (round to the nearest penny).
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = the cost of iced tea the 1st week
Let +b+ = the cost of a veggie burger the 1st week
Let +c+ = the cost of the fries the 1st week
----------------------------------------------
(1) +a+%2B+b+%2B+c+=+756+ ( in cents )
(2) +c+=+2a+ ( in cents )
(3) +1.1a+%2B+1.25b+%2B+c+=+868+ ( in cents )
--------------------------------------
Multiply both sides of (3) by +100+
(3) +110a+%2B+125b+%2B+100c+=+86800+
Multiply both sides of (1) by +100+
and subtract () from (2)
(3) +110a+%2B+125b+%2B+100c+=+86800+
(1) +-100a+-+100b+-+100c+=+-75600+
------------------------------------
(4) +10a+%2B+25b+=+11200+
Substitute (2) into (1)
(1) +a+%2B+b+%2B+2a+=+756+
(1) +3a+%2B+b+=+756+
Multiply both sides of (1) by +25+ and
subtract (4) from (1)
(1) +75a+%2B+25b+=+18900+
(4) +-10a+-+25b+=+-+11200+
----------------------------
+65a+=+7700+
+a+=+118.46+
and
(2) +c+=+2a+
(2) +c+=+236.92+
and
(1) +3a+%2B+b+=+756+
(1) +3%2A118.46+%2B+b+=+756+
(1) +355.38+%2B+b+=+756+
(1) +b+=+400.62+
-----------------------------
Convert to dollars since answers are in cents:
+a+=+1.18+
+b+=+4.01+
+c+=+2.37+
The cost of iced tea the 1st week was $1.18
The cost of a veggie burger the 1st week was $4.01
The cost of the fries the 1st week was $2.37
------------------
check the answers:
(1) +a+%2B+b+%2B+c+=+7.56+ ( in dollars )
(1) +1.18+%2B+4.01+%2B+2.37+=+7.56+
(1) +7.56+=+7.56+
and
(2) +c+=+2a+
(2) +2.37+=+2%2A1.18+
(2) +2.37+=+2.36+
close enough
and
(3) +1.1a+%2B+1.25b+%2B+c+=+8.68+ ( in dollars )
(3) +1.1%2A1.18+%2B+1.25%2A4.01+%2B+2.37+=+8.68+
(3) +1.298+%2B+5.0125+%2B+2.37+=+8.68+
(3) +8.6805+=+8.68+
OK when rounded off