30+5=5+30 with commutative property or 30+5=35
By solving the equation
1/2 +x =4/7
x = 4/7 -1/2
x= 1/14
For C at 7pm they sold most and at 6 am they sold less

Actually Welcome to the Concept of the Surface Areas and Volumes.
Since, Volume of cone = 1/3 π r^2 h,
here, r = 10 Inches and h= 12 inches, also π =3.14
so, VOC = 1/3 π (10)^2 × (20)
VOC = 1/3(3.14)(100)(20)= 2093.33 inch^3
=> so the volume of the cone is 2093.33 cubic inches.
-7/4:-1.75
2/5:0.4
-1.75=0.4t
-1.75/0.4=t
-4.375=t
Hope I helped you well, have a victorious day!