thirty是什么意思,thirty怎么读

陕西旅游版小学英语四年级下i have breakfast at seven thirtyppt
twenty-eight twenty-nine thirty thirty-one
词2-9后加ty,其中要注意 20,30,40,50,80的拼写:20 twenty ,30 thirty
twenty thirty fourty fifty sixty ……中哪些是念"ty "?哪些是
外研社七上module3unit 1there are thirty students