Modeling
Using Linear Systems
Example Continued
Step 3. Solve the system of equations using one of the methods discussed earlier.
Another method would be substitution.
0.25x + 20 = 0.08x + 40
0.25x = 0.08x +20
0.17x = 20
x = 117.65
y = 0.25(117.65) + 20
y = 49.41
The solution point is (117.65, 49.41)
Step 4. Interpret the solution.
Annie's solution will depend on how many minutes she plans to talk. At 118 minutes the plans basically cost the same. Less than 118 minutes Vendafone is cheaper and greater than 118 minutes Sellnet is cheaper.