This ticket machine is broken. 这台售票机坏了。

(1) 改为疑问句 

—> Is this ticket machine broken?

(2) 句子开头加 I wonder if 我想知道是不是……/ 我怀疑是否……

—> I wonder if this ticket machine is broken.

(3) 改为以 someone “有人/某个人”为主语的主动式句子，时态为过去时

—> Someone broke this ticket machine. 有人把这台售票机弄坏了。

There are no seats on the bus. 公共汽车上没有空位。

(1) 将 no 改为 some 的肯定句

—> There are some seats on the bus.

(2) 改为疑问句

—> Are there no seats on the bus? 公共汽车上没有空位吗？/

      Are there any seats on the bus? 公共汽车上有空位吗？

(3) 改为用 must “应该……”做助动词的句子

—> There must be no seats on the bus.