For a basic monthly fee of F yen (¥F), Naoko's first cell phone plan allowed him to use a maximum of 420 minutes on calls during the month. Then, for each of x additional minutes he used on calls, he was charged ¥M, making his total charge for the month ¥T,where T= F+ xM. What is the value of F?
(1) Naoko used 450 minutes on calls the first month and the total charge for the month was ¥13,755.
(2) Naoko used 400 minutes on calls the second month and the total charge for the month was ¥13,125.
（2）400＜420,so 13125=F+0*M, sufficient
2018-02-25 23:22:37 回复