So you can do this by using a system of equations x=student tickets y=adult tickets
x+y=394 x+56=y then you substitute y in x+(x+56)=394 2x+56=394 2x=394-56 2x=338 x=169 which is the number of student tickets then you find the amount of adult tickets x+56=y 169+56=y 225=y and now you can check it 225+169=394 394=394
Answer: 169 student tickets were sold 225 adult tickets were sold