Surveys conducted in american high schools concluded that 90% of the students in a sample of 400 students had more than one active email account. what would the margin of error be for the population proportion?
a.) 1.5%
b.) 3%
c.) 4.5%
d.) 9%

Which one ? is the answer and how to find this answer

Amir wants to proportionally increase the size of a photo to create a poster for his room. the size of the original photo is shown. complete the statement and then answer the question to represent ways that amir can increase the size of his photo.

Determine if the equation defines y as a function of x: 2xy = 1. yes o no