What image of abc is abc what transformations would result in

What number should be added to both sides of the equation to complete this square? x^2-10x=7

Jackie purchased 3 bottles of water and 2 cups of coffee for the family for $7.35. ryan 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?

How do i do this activity, is appreciated