Simplify:
a) 3y - y
b) 69 + 4 - 9 +5

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?

Find the solution of this system of equation -7x+y=-20 9x-3y=36

Polygon abcde is reflected to produce polygon a′b′c′d′e′. what is the equation for the line of reflection?