High School A currently has 900 students and is projected to grow by 50 students each year.
We can write an equation using the above information

Where A represents the number of students in High School A in t years.
High School B currently has 500 students and is projected to grow by 100 students each year.
We can write an equation using the above information

Where B represents the number of students in High School B in t years.
Let us graph these two equations
Determine which high school is projected to have more students in 4 years.
Let us substitute t = 4 into both equations

High school A is projected to have 1100 students in 4 years.

High school B is projected to have 900 students in 4 years.
Therefore, high school A is projected to have more students (1100) as compared to high school B (900) in 4 years.