Which html attribute specifies an alternate text for an image, if the image cannot be displayed?

Part A)

Using the Pythagorean theorem you can find the height:

17^2 = 8^2 + x^2

289 = 64 +x^2

x^2 = 289 - 64

x^2 = 225

x = √225

x = 15

The height is 15 cm.

Part B)

Area of the triangular side: 1/2 x 16 x 15 = 120 square cm.

There are two triangles so 120 x 2 = 240 square cm.

One side = 20 x 17 = 340

There are 2 sides so 340 x 2 = 680 square cm.

The bottom is 16 x 20 = 320 square cm.

Total cardboard needed: 240 + 680 + 320 = 1,240 square cm.