讲解一下这道题**Textual Information:** * **Other Relevant Text:** * Numbers labeling sides/height: 17, 20, 15, 15 (green), 20 (green). * Caption below image: SAT数学经典题型破解 (上) SAT如何高效备考? 专业SAT家教 ... 访问 > **Chart/Diagram Description:** * **Type:** Geometric figure (Trapezoid, likely a right trapezoid). * **Main Elements:** * A four-sided figure is shown, resembling a trapezoid. * The figure has a top horizontal side with length labeled as 20. * It has a right vertical side with length labeled as 15. * It has a bottom horizontal side with length labeled as 20 (in green text). * It has a left slanted side with length labeled as 17. * A dashed blue vertical line is drawn from the top left vertex perpendicular to the bottom base. This line represents the height. * The dashed blue line (height) is labeled with green text "15". * A red square symbol at the bottom of the dashed blue line indicates a right angle between the height and the bottom base. * Implicitly, there is a right angle at the bottom right corner due to the vertical right side and horizontal bottom base. * Green curved lines/arcs are present near the vertices but are not clearly defined.