I have to find the slope

This race was first held in 1953 on august 16th. every decade the race finishes with a festival. how many years is this?

Jackie purchased 3 bottles of water and 2 cups of coffee for a family for $7.35. brian bought 4 bottles of water and 1 cup of coffee for his family for $7.15. how much does each bottle of water cost? how much does each cup of coffee cost? i need this done

Ijust need to see how to do this. so you don’t have to answer all of them just a step by step explanation of one.