I believe it is irrational. The answer comes out to 4.942809041582063......
7.1 is the correct answer
Step-by-step explanation:
A U B means all values containing in A and B.
Therefore A U B = {3,6,7,11,12,15} (C)
You can put the 2points into a graph in your calculator and do the slope y1~mx1+b it will give you your equation which is y= 2x - 2