787,000 in scientific notation

Twenty-five percent of the customers entering a grocery store between 5 p. m. and 7 p. m. use an express checkout. consider five randomly selected customers, and let x denote the number among the five who use the express checkout.

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

What makes a trapezoid an isosceles trapezoid?