1. **Problem statement:** We need to find how many triangles are formed in a trapezoid divided into four horizontal layers by three parallel lines, with one diagonal from the top-left to the bottom-right vertex. 2. **Understanding the figure:** The trapezoid is divided into 4 horizontal strips by 3 parallel lines. The diagonal line crosses from the top-left vertex to the bottom-right vertex. 3. **Counting triangles:** Each horizontal layer is intersected by the diagonal, creating smaller triangles. 4. **Triangles in each layer:** - The top layer has 1 triangle. - The second layer has 2 triangles. - The third layer has 2 triangles. - The bottom layer has 1 triangle. 5. **Total triangles:** $$1 + 2 + 2 + 1 = 6$$ 6. **Answer:** There are 6 triangles in the figure.