25400

We started by looking at the 2 bottom rows and looked at what was different and what was the same. From that we noticed that the square had to be 2 more than the triangle because 20 was two more than 18, then the only number that the circles could be was 4. The square had to be 8 and the triangle was 6. Then the only shape left was the Hexegon and we knew what the square was so the Hexegon had to be 7. We added up the column with the missing answer and the answer was 21. We enjoyed working this out!