To calculate the Taxi fare, we need to sum the fixed charge and the additional charge. Fixed charge ever is $1.75. The additional charge changes with the miles traveled (one mile costs $0.45, two miles $0.90, and so on), so we need multiply the charge ($0.45) by the miles m traveled.
1.75 + 0.45 m
The problem says that the fare was equals to $13.90 so the final equation is
