159322

I knew if I wanted to find the mystery number I would have to figure out all the shapes. I started with the circles because the third & fourth columns vertical both had 3 circles and the 2 column totals had a difference of 2 so that had to be the difference between the square and triangle, so once I figured out the circle. I added them in the columns and then subtracted them by the result of that column which gave me the number of a square and triangle. I figured out the circles by trial and error. I knew if I figured out the square and the triangle all I would be left with is the hexagon and that answer came easily because all I had to do was add the squares and minus them by the total of the columns which was 30 so the hexagons had to be 7.