company a = 22 + 0.07m
company b = 8 + 0.12m
We are looking for the time when the prices are equal. i.e. the price of company a = the price of company b
company a = company b
22 + 0.07m = 8 + 0.12m
22 - 8 = 0.12m - 0.07m
14 = 0.05m
m = 14/0.05
m = 280
Therefore, the two companies will cost the same if you talk for 280 minutes