15. If 1.2 is the average of 0.2, 0.8, 2.2, and x, what is the
numerical value of x?
+

ca = ec

cpctc makes it so that corresponding parts of the triangle you proved to be equal are equal, the other options aren't part of the part of the triangles you proved to be equal.

take the logarithm of both sides (the base of the log doesn't matter):

apply the exponent property - this says that :

distribute the log terms on both sides:

group like terms together:

divide through both sides by the coefficient on :

you can do some additional rewriting here using the properties of the logarithm to simplify things if you like:

there were only 2 presidents that were under the age of 45. theodore roosevelt, and jfk, that makes 5%