In a certain state, speeding fines are determined by the formula Upper F equals 5 left parenthesis x minus 60 right parenthesis plus 75F=5(x60)+75,

where F is the cost, in dollars, of the fine if a person is caught driving x miles per hour. Use this formula to determine how fast a person was speeding if the fine comes to $ 100.$100.

The person was driving ???

miles per hour.