Plz help me with this

Solve the system of equations. y= 2x y= x^2 - 15

Rockwell hardness of pins of a certain type is known to have a mean value of 50 and a standard deviation of 1.1. (round your answers to four decimal places.) (a) if the distribution is normal, what is the probability that the sample mean hardness for a random sample of 8 pins is at least 51?

Which of the following best describes the delian problem?