General Intelligence · Number Triangles

In a number puzzle triangle, the top vertex contains 3, the bottom-left vertex contains 2, and the bottom-right vertex contains 1. If the value inside the triangle is determined by subtracting the bottom-right value from the top vertex and then adding the bottom-left value, what value replaces the '?' if the center value is to be calculated under the same rule with top = 4, left = 2, and right = 3?