Hi there!
Let t be the number of teachers
Let a be the number of administrators
t+a=24
35,000t+40,000a=860,000
a=24-t
35,000t+40,000(24-t)=860,000
35,000t+960,000-40,000t=860,000
35,000t-40,000t=860,000-960,000
-5,000t=-100,000
t=-100,000/-5,000
t=20
a=24-t
a=24-20
a=4
Therefore there are 4 administrators and 20 teachers.
Hope this helps!