Answer: it will take 200 additional minutes for the two plans to cost the same.
Step-by-step explanation:
Let x represent the number of additional minutes it will take for the the two plans to cost the same.
Cingular's plan charges $39.99 per minute with additional minutes costing $0.45. This means that the total cost of x additional minutes would be
39.99 + 0.45x
Verizon's plan costs $44.99 with additional minutes at $0.40. This means that the total cost of x additional minutes would be
44.99 + 0.4x
For the the two plans to cost the same, the number of additional minutes would be
39.99 + 0.45x = 44.99 + 0.4x
0.45x - 0.4x = 44.99 - 39.99
0.05x = 10
x = 10/0.05
x = 200
