math
posted by Sonji on .
Find out how many calls must be made to make Plan A the better deal.
• Plan A: $45 a month for unlimited calling Plan B $15 a month .10 per min.
I need to write a cost equation for plan A and for plan B then I need to solve.

Plan A: cost = 45
Plan B: cost = .10x + 15, where x is the number of minutes
You want to know when
.10x + 15 > 45
x + 150 > 450
x > 300
check:
for 299 minutes:
PlanA = 45
PlanB = 29.90 + 15 = 44.90
...... Plan B is still better
for 301 minutes:
Plan a = 45
PlanB = 30.10 + 15 = 45.10
.... Plan A is better for x > 300