Okay, let's solve this step-by-step:
a)
Length = 30 in = 2.5 ft
Width = 15 in = 1.25 ft
Height = 18 in = 1.5 ft
Volume (cubic ft) = Length x Width x Height
= 2.5 x 1.25 x 1.5 = 3.75 cubic ft
Volume (cubic yards) = 3.75 / 27 = 0.14 cubic yards
b)
Since the box volume is 3.75 cubic ft and potting soil bags are 1.5 cubic ft,
you will need 3.75 / 1.5 = 2.5 bags of soil.
Each bag weighs 11.2 lbs, so 2.5 bags will weigh 2.5 * 11.2 = 28 lbs of soil.
c)
To paint the sides of the box, you need:
Length (2 sides) = 30 in x 2 = 60 in
Width (2 sides) = 15 in x 2 = 30 in
Height (4 sides) = 18 in x 4 = 72 in
Total inches of sides = 60 + 30 + 72 = 162 in
Conversion: 162 in / 12 in = 13.5 square ft
So you will need about 14 square feet of paint.
Let me know if you have any other questions!