I'd start with setting up the equations. Calling x the number of students in most popular country 1, and y in country 2.
x + y = 44740
x - y = 5672
now solve for x1 and x2. You can subtract second from first:
0 + 2y = 39068
y = 19534
so
x = 5672 + 19534 = 25206
Add a sentence to answer it in words.