Final answer:
The equation c=25m+45 represents a linear equation, where c represents the monthly cost and m represents the minutes used. There is not a proportional relationship between minutes and cost.
Step-by-step explanation:
The equation c=25m+45 represents a linear equation, where c represents the monthly cost and m represents the minutes used. To determine whether there is a proportional relationship between c and m, we can check if the ratio between c and m remains constant for different values of m.
In this case, the equation is not in the form y=kx, where k is a constant. Therefore, the relationship between c and m is not proportional. The cost does increase as the minutes increase, but it does not increase at a constant rate.