Solve the equation. 0.3b = 8.1

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?

Which shows the correct solution of the equation 1/2a+2/3b=50, when b=30?

Use composition to determine if (x) or h(x) is the inverse of f(x) for the limited domain x2-1.