Hey!
You have to divide the total amount she has by the surface area.
Surface area = 2(wl+hl+hw)
That gives you:
[tex] (15 + 18 + 30) \times 2 \\ 63 \times 2 = 126 [/tex]
The surface area is 126 ft. Now divide the total amount she has by the surface area.
[tex] 1,134 \div 126 = 9 [/tex]
That means she can cover 9 boxes
[tex] \framebox{She can cover 9 boxes} [/tex]
