Using diagonals from a common vertex, how many triangles could be formed from a 15-gon?

Mrs.renoir has completed the interior portion of a quilt top measuring

The height of a flare fired from the deck of a ship in distress can be modeled by h(t)= -2(8t^2-52t-28), where h is the height of the flare above water and t is the time in seconds. a. find the time it takes the flare to hit the water.

The standard deviation for a set of data is 5.5. the mean is 265. what is the margin of error?