Every 6 days John eats 20 ounces of cereal. At the same rate, how many ounces of cereal will John eat in 15 days?

At a local museum, the total price for one adult and one child is $11. mrs. smith paid for herself and her three children. she spent $19. record the system of equations to be solved and then find the price of an adult and child ticket using either elimination or substitution.