What is the cost

Question

At a store 10 bottles of soda and 5 bags of chips cost 22.50. 2 bottles of soda and 4 bags of chips cost 11.10. What is the cost of a single bottle of soda?

Answer 1

What is the cost

At a store 10 bottles of soda and 5 bags of chips cost 22.50.
2 bottles of soda and 4 bags of chips cost 11.10.
What is the cost of a single bottle of soda?

10s + 5c = 22.50
2s + 4c = 11.10

2s + 4c = 11.10
2s = -4c + 11.10
s = -2c + 5.55

10s + 5c = 22.50
10(-2c + 5.55) + 5c = 22.50
-20c + 55.50 + 5c = 22.50
-15c = 22.50 - 55.50
-15c = -33.00
c = 2.20   <<<<<<<<<<<<<<<<<<

2s + 4c = 11.10
2s + 4(2.20) = 11.10
2s + 8.80 = 11.10
2s = 11.10 - 8.80
2s = 2.30
s = 2.30 / 2
s = 1.15   <<<<<<<<<<<<<<<<<<

Check:

10s + 5c = 22.50
10(1.15) + 5(2.20) = 22.50
11.50 + 11.00 = 22.50
22.50 = 22.50