Given that Verizon charges a base fee of $20 per month plus an additional charge for each minute the customer uses. The monthly phone cost, C, can be represented with the equation C = 20 + a(m), where a is the additional charge per minute, and m is the number of minutes used.
We have to find the equation that can be utilized to find the number of minutes a customer used if we know a and C.
Now, we have to solve for m:

Thus, option A is correct.
2nd part:
Given that Alicia paid $30 and used 500 minutes.
So, the value of C is 30 and m = 500. So,

Thus, the additional charge per minute is $0.02 per minute.