Solve for x

s = 2rx-4

Given the following sampling distribution of one mean with a sample size 49, from a normally distributed population,find the population standard deviation, o.79828588912497

Which three lengths could be the lengths of the sides of a triangle? 21 cm, 7 cm, 7 cm 9 cm, 15 cm, 22 cm 13 cm, 5 cm, 18 cm 8 cm, 23 cm, 11 cm

Need on this geometry question. explain how you did it.