What postulate or theorem justifies the statements?

Asimple random sample of size nequals14 is drawn from a population that is normally distributed. the sample mean is found to be x overbar equals 70 and the sample standard deviation is found to be sequals13. construct a 90% confidence interval about the population mean

The reflexive property of congruence lets you say that ∠pqr ≅

How are sas and sss used to show that two triangles are congruent?