Which equation would you use to solve the following situation? There are 6 cookies in the cookie jar. Sean bakes some more and now there are 15 cookies in the jar. How many cookies did Sean bake?

6 + x = 15.
x - 6 = 15.
15 + 6 = x.
6 - x = 15.

Aman steps out of a plane at a height of 4,000m above the ground falls 2,000m very quickly and then opens his parachute and slowly falls the remaining 2000m to the ground what height above the ground would be the best choice for a reference point

Imogene invested $8,000 in a bank account that pays 8 percent simple interest at the end of each year. her friend invested the same amount in stocks where the growth of the investment is represented as 2,000 times the square root of 2 less than the time lapsed in years. if y1 and y2 represent the amount earned in dollars and t is the time lapsed in years, which system of equations correctly represents the situation?

The perimeter of a movie screen is 54 meters. the screen is 18 meters wide. how tall is it?