题目

The twins, who(finish)their homework,were allowed to play badminton in the playground. 答案：【1】had finished在一幅长80cm，宽50cm的矩形风景画的四周镶一条金色纸边，制成一幅矩形挂图如图所示．如果要使整个挂图的面积是5400cm2，设金色纸边的宽为xcm，则可列方程                    ．