This is probably not how you do it, but,...
I did 25 (students) x 7 = 175 (students)
So then I did 18 x 7 = 126
so the answer is C) 126 students.
But if your teacher or whoever wants to know how to do it correctly and show the work correctly then don't do what I did because they may take off points (if they're strict...) (and that probably didn't make any sense but whatever...) Hoped this helped! :)