What is the estimate for 5.29+6.78

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?

If f(x)=3x+1 and f^-1=x-1/3, then f^-1(7)=

An equation in slope-intersept form the lines that passes thought (-8,1) and is perpindicular to the y=2x-17.