It is important to have a close look at all the information's that are already given in the question.Based on those information's the answer to the question has to be determined.
Total amount of calorie in 20 ounce of smoothie = 450
Then
Total quantity of calorie in 1 ounce of smoothie = 450/20
= 45/2
= 22.5 calorie
So 22.5 calorie is present in 1 ounce of smoothie bought by Javier. I hope this is the answer you were looking for and the procedure for solving is also clear to you.