A trapezium has both diagonals and two upright lines dropped from its top corners to the base. How many triangles does the figure contain?

On each side: 3 in the strip between the slanting side and the upright line, 2 using the upright line and the diagonal from the far top corner, 2 using the slanting side and that diagonal, and 2 standing on the whole base with that top corner as apex, 9 per side, 18. On the middle line: the top triangle between the diagonals and the bottom one on the base, 2. Total $18+2=20$.