Aquarium is 17 in long, 9 in wide, 11 inches tall. How much glass do they need to buy to enclose the aquarium?

To enclose the aquarium with glass, they will need enough glass to cover the four sides of the aquarium.

The formula to calculate the surface area of a rectangular prism (which an aquarium resembles) is:
Surface Area = 2lw + 2lh + 2wh

Where:
l = length
w = width
h = height

Given:
l = 17 inches
w = 9 inches
h = 11 inches

Plugging in the values:
Surface Area = 2(17)(9) + 2(17)(11) + 2(9)(11)
Surface Area = 306 + 374 + 198
Surface Area = 878 square inches

Therefore, they will need to buy 878 square inches of glass to enclose the aquarium.