Help, please

oh right, because I didnt know how the angle of elevation of the driveway in the first place, thank you I know what function

OK...a 15% grade means that for every 100 ft of horizontal distance, the driveway rises 15 ft. vertically.....

Does that give you a clue about which function you should use??? Hint: It will be an "inverse" one ......

I'm thinking I would use arccos.

Think about this..... the angle of elevation involves - in this case - the side adjacent to the angle and the side opposite the angle...does that help???