m = the number of miles driven
Company A cost = 76
[they charge $76 for unlimited mileage, so they don't charge by the miles driven]
Company B cost = 0.70m + 55
[they charge an initial fee of $55 plus $0.70 per mile(m)]
For what mileages will Company A charge less than Company B?
Company A cost < Company B cost -----> 76 < 0.70m + 55
To solve for m, isolate/get the variable "m" by itself in the inequality:
76 < 0.70m + 55 Subtract 55 on both sides
76 - 55 < 0.70m + 55 - 55
21 < 0.70m Divide 0.70 on both sides to get "m" by itself
30 < m [m is any number greater than 30]
Company A will charge less than Company B for mileages over/greater than 30.