The coefficient is always between which two numbers

Each equation given below describes a parabola. which statement best compares their graphs? x = 2y^2 x = 8y^2

Tim's phone service charges $26.39 plus an additional $0.21 for each text message sent per month. if tim's phone bill was $31.64, which equation could be used to find how many text messages, x, tim sent last month?

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