Answer:
700 Minutes
Explanation:
For this problem, we need to write an expression that represents the cost per the amount of time used for each phone plan, and set the two expressions equal to each other to find how many minutes would be needed for the costs to be equal.
For the first phone plan, we have a base $28 and additional $0.09 per minute of call. This can be expressed as:
28 + 0.09x Where x is the number of minutes used
For the second phone plan, we have a flat $0.13 per minute of call. This can be expressed as:
0.13x Where x is the number of minutes used
To find how many minutes would be used to make the cost equal, we simply set these expressions as equivalent, and solve for x.
28 + 0.09x = 0.13x
28 + 0.09x + -0.09x = 0.13x + -0.09x
28 = 0.04x
28 = (1/25)x
28 * 25 = (1/25)x * 25
28 * 25 = x
700 = x
Thus, for the cost of these phone plans to be equal, you would have to use 700 minutes per month.
Cheers.