Over the weekend, Brady and Jack drove to Key West to go scuba diving. Now they're preparing to go home. Brady needs gas for his jeep, which gets 25 miles per gallon for gas mileage. When he stops at the gas station, he already has 6 gallons of gas in his tank. He buys more gas for $1.25 per gallon.
Find the number of miles that Brady can drive, d(s), as a function of the amount he spends on gas, s.
d(s) = _____________________