Problem 24 (2001 AMC 8)

Each half of this figure is composed of $3$ red triangles, $5$ blue triangles and $8$ white triangles. When the upper half is folded down over the centerline, $2$ pairs of red triangles coincide, as do $3$ pairs of blue triangles. There are $2$ red-white pairs. How many white pairs coincide? [See figure in original PDF]