therearethirtystudentsinourclass改为否定句

there are no thirty students in our class.
There be句型的否定式的构成和含有be动词的其它句型一样,在be后加上not或no即可.
注意not和no的不同：not是副词,no为形容词,not a/an/any + n.相当于no+ n..例如：
There are some pictures on the wall.→There aren't any pictures on the wall.=There are no pictures on the wall.
There is a bike behind the tree.→ There isn't a bike behind the tree.=There is no bike behind the tree.

The number of students in our class is not thirty.

there aren'tthirtystudentsinourclass

There aren't thirty students inour classroom。