Question

A restaurant charges $12 for a buffet plus $2.60 for each drink. Another restaurant charges $15 for a buffet plus $2 for each drink. The system of equations is graphed below.

https://go.flvs.net/courses/1/flvs_79_3600_cffc0c151398115/ppg/educator_math3/v10/04_09_98.jpg


Part 1: What is the solution?
Part 2: Show your work to verify the solution for both equations.

Answer 1

Let C be cost, d be num of drinks

C = 2.6d +12
C = 2d +15

solution is where they intersect or have equal costs
2.6d +12 = 2d +15
-2d -2d
-----------------
0.6d +12 = 15
-12 -12
-----------------
0.6d = 3
--- --
0.6 0.6

d = 5

So when they order 5 drinks, the cost is $25 at either restaurant