Plz help I’ll mark you

To describe a sequence of transformations that maps triangle abc onto triangle a"b"c", a student starts with a reflection over the x-axis.how should the student complete the sequence of transformations to map triangle abc onto triangle a"b"c"? plz

What is the number 321,000,000 in scientific notation? also what is the number? ?

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