The price of a 7-minute phone call is $2.45. What is the price of an 18 -minute phone call?

According to Question ,The price of a 7-minute phone call is $2.45 . And we need to find the price of a18 minute phone call . So we will use unitary method here ,

Here it was a case of direct proportion in which if two things are directly proportional to each other. If one thing thing increases then the value of second also increases. Here if the time increases then the cost also increases.