Tom and peter's 后面加 car 还是加cars

为什么“I like toy cars”中car要加“s”? you can keep the cars 为什么car要加s 是Tom's and Peter's bikes还是Tom and Peter've bike Tom's and Mary's room后面的room要不要加S,Why? t后面加s还是加es let's后面加动词还是名词 photo复数后面加es还是s often后面加动词原形?还是加s? 英文：“mango”后面加es还是加s? 单三后面动词加s还是加ed (Mary and Tom)math teacher 's 应该加在哪? Tom and Bob are classmate要加s吗