Which process most likely formed a layer of the sedimentary rock gypsum?

Gypsum originated 200 million years ago as a result of marine deposits when part of what are now our continents were immense oceanic extensions. During this period some seas were dried leaving plaster beds that were covered to be discovered later by man. Since the time of memory plaster has coexisted with humanity and constitutes one of the oldest building materials.

2. x2 + 8x + 12 = 0 to prove: x = -6 or x = -2

The area of the indian subcontinent is 4.4 million km^2 whereas the usa is  9.8 million  km²