Seventy percent of the 100 students in middle school cafeteria bought their lunch sone of the students that brought there own lunch leave the cafeteria to attend a assembly now only 60% of the remaining students bought their lunch how many students are remaining in the cafeteria

So we solve for each

70% of 100=70

students who didn't buy lunch=100-70=30

some of the 70 left so that the students who bought lunch, are 60% of those who are left

we know that the students who didn't buy lunch didn't change number so therefor

100% of students left-60%=40% = students that didn't buy lunch=30 so

40%=30

20%=15

100%=75

there were 75 students lfet in the cafeteria