A circle, a rectangle and a triangle overlap. Find the sum of the numbers in the circle minus the sum of the numbers in the triangle.

Circle: $9+5+12+3=29$. Triangle: $4+12+8+3=27$. Difference $=29-27=2$. 5 compares only the single parts $9-4$, −2 subtracts the wrong way, and −1 subtracts the rectangle's sum $14+5+8+3=30$ instead of the triangle's.