Answer:
See below in bold.
Explanation:
Linear model:
E = 24x + 840 where E is the enrolment .
If there are 900 students then
900 = 24x + 840
24x = 900-840 = 60
For E < 900 we have the inequality
24x < 60
x < 2.5
As we are dealing in years our answer is
x < 3 years .