在一个笼子里面放着几只鸡与几只兔，数了数一共有14个头，44只脚．问鸡兔各有几只？设鸡为x只，得方程（  ）

革命或改革往往是某种旧制度阻碍社会经济的发展而发生的，懂得改变，是一种智慧。阅读下列材料，结合所学知识，回答问题。
材料一 什么力量迫使他们搞改革呢？这就是把俄国拖上资本主义道路的经济发展的力量。地主农奴不能阻挠俄国同欧洲商品交易的增长，不能保持住旧的崩溃的经济形态，如克里米亚战争显示出农奴制俄国的腐败和无能。解放以前，农民的“叛乱”每十年都要高涨一次。这使头号大地主亚历山大二世也不得不承认，从上面解放比等待从下面推翻要好些。                              ——列宁《“农民改革”和无产阶级农民改革》
材料二 日本的新统治者致力于日本社会的转型，以获得同外国势力在政治和军事上的平等地位。……变革使日本成为东亚的政治、军事和经济强国……明治政府的首要目标是强化中央集权……               ——摘自杰里·齐格勒《新全球史》（第三版）下
材料三  1831年的一天，在美国南方城市新奥尔良的奴隶拍卖市场上，奴隶主们正用皮鞭毒打黑奴，还用烧红的铁条烙他们，一位北方来的年轻水手看到眼前的悲惨景象，愤怒地说：“太可耻了！等有了机会，我一定要把这奴隶制度彻底打垮！”1861年他当上了美国总统，实现了这个伟大的抱负。
（1）从材料一归纳出俄国实行农奴制改革的原因。（不得照抄原文）
（2）材料二中“变革”指的是什么历史事件？为了实现材料二中的“首要目标”，日本政府采取了什么措施？
（3）材料三中“北方来的年轻水手”是谁？他为美国资本主义的发展扫清什么障碍？
（4）土地是人类社会最早、最基本的生产资料，19世纪60年代，美国、日本、俄国三国发生的革命或改革，都废除了阻碍其发展的旧的土地制度，产生了深远的历史影响。三国解决土地问题采取的措施分别什么？
（5）综合以上材料，结合所学知识，分析这三次革命或改革对这三国的共同作用。

    As a child, I started learning to play the piano, my favorite musical 1 but I was forced to give up when I started my middle school2 I could concentrate more on my studies.

    It's one of my biggest3 to stop practicing the piano when I recall sadly today. During the following years, I kept telling my piano teacher that I would4However, I didn't keep my promise because I was 5 with my study6 I lost touch with my teacher. Some years later, my teacher died. I was very sad because I lost such a good teacher. She was a very warm and gentle person. It hurts me to think she may have been 7 that I never returned. I haven't taken lessons since then but to be honest, I 8 to. Sitting at the piano, I couldn't help recalling many 9 ---times of my practising at home and playing before my teacher and one time my teacher 10 me after I played entire pieces of music wrong in front of her colleagues. I was so 11 that I could hardly say anything. But her 12helped ease my shame. These memories13good or bad, never caused my14 for playing the piano again.

    This thought then led me to think that 15 is like music, and that we all try to play different 16 in the instrument of our life. Sometimes the pitch (音高) is17when we play it well, but sometimes we are out of tone. However, we all continue to create our own 18style of music. No matter what style our music is, it is 19 that we sing the songs of joy, quietness and love. Though I may never make it back to piano lessons, it doesn't 20 that I've stopped making music.