May anyone please help me?

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?

3x + 4y = 5 x- 3y = -7 solve by substitution

Which expression and diagram represent “renee biked four times as far this month as last month”?