Question 21309
students = x
non-students=y
x+y=410
y=410-x

3x+7y=1650
3x+7(410-x)=1650
3x+2870-7x=1650
-4x=-1220 (divide both sides by -4)
x=305        y=410-305=105

Hence, 305 students attended and 105 non-students attended