A trapezium has both diagonals drawn, and a line runs across it halfway down, parallel to the top and bottom sides. How many triangles are in the figure?

Without the middle line, a trapezium with its diagonals has 8: top, bottom, the two side pieces and four halves. The middle line adds a tiny triangle under the crossing point, two at the left and right ends of the line, and two whose apex is a top corner: 5. Total $8+5=13$.