Can someone help explain how I get the answer for this? S=R-rR solve for R

Points d and e are midpoints of the sides of triangle abc. the perimeter of the triangle is 48 units. what is the value of t? ο ο ο ο 7t +

Anormally distributed data set has a mean of 176.3 and a standard deviation of 4.2. what is the approximate z-score for the data value of 167.9? 2.00 −2.00 8.4 −8.4

Which expression is equivalent to 64 - 9x^2?