We need to find the first five numbers of a sequence determined by the expression:
Notice that each time we increase the value of x by 1 unit, we add 12 to the previous result. Thus, subsequent terms in the sequnce differ by 12 units.
From the options, the only one with all the terms differing by 12 units is the beginning at x=1:
Therefore, the answer is: C. 18, 30, 42, 54, 66