We have: 30 students have lived in Texas less than a year 

=> There are 5% students of 600 students at Goodnight Middle School in Texas have lived here less than 1 year.

So there 65% students are not native Texas lived here less than a year and more than 10 years.

But there are 85% are not native Texas 

=> The non-native students have lived more than 1 year but less than 10 year is 20% = 120(students)