How do i use the substitution method when trying to find the x or y values, in an algebraic equation

Farnesene is a sesquiterpene. how many different isomers arising from double-bond isomerizations are possible? g

The measure of one angle of an octagon is two times smaller that of the other seven angles. what is the measure of each angle?

Afactory makes propeller drive shafts for ships. a quality assurance engineer at the factory needs to estimate the true mean length of the shafts. she randomly selects four drive shafts made at the factory, measures their lengths, and finds their sample mean to be 1000 mm. the lengths are known to follow a normal distribution whose standard deviation is 2 mm. calculate a 95% confidence interval for the true mean length of the shafts. input your answers for the margin of error, lower bound, and upper bound.