68.26% out of 90 students is how many students?

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

What expression is equivalent to 42x-56y

Can someone check if i did this correct. it’s number 4 if you’re wondering.