摘要
几年以前，我在门前的小院种植了一棵7英尺的小树，这棵小树每年长3英尺，现在已是原来高度的4倍，问，树有多高？它是我多少年前种植的？
Several years ago,I planted a 7-feet tree in my front yard.The tree has grown 3 feet each year,and last year it was four times the original height.How tall is the tree now,and how long ago did I plant it？
