Let x be the total minutes used Total cost = 40 + 0.45(x - 700)
------------------------------------------------------------------ Form the equation and solve x ------------------------------------------------------------------ 40 + 0.45(x - 700) = 48.10 40 + 0.45x - 315 = 48.10 0.45x - 275 = 48.10 0.45x = 48.10 + 275 0.45x = 323.10 x = 323.10 ÷ 0.45 x = 718
------------------------------------------------------------------ Answer: John had used 718 mins this month ------------------------------------------------------------------