Sydney took a taxi from her house to the airport. The taxi company charged a pick-up fee of $1.60 plus $1.75 per mile. The total fare was $20.85, not including the tip. Write and solve an equation which can be used to determine xx, the number of miles in the taxi ride.
a) $1.75x + $1.60 = $20.85
b) $1.75x - $1.60 = $20.85
c) $1.75x + $1.60 = $20.85 + tip
d) $1.75x - $1.60 = $20.85 + tip