You would use a system of equations.
A= adult tickets sold
S= student tickets sold
A+S=400
5A+3S=1360
-3(A+S=400)= -3A-3S=-1200 +
5A+3S=1360 =
2A = 160 so A=80
now when you plug 80 into the original equation you get 80 + S = 400 so S=320
80 Adult tickets were sold and 320 student tickets were sold.
