Two options:
First option - list everything (waste time)
6, 10, and 14
6: 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72, 78, 84, 90, 96, 102, 108, 114, 120, 126, 132, 138, 144, 150, 156, 162, 168, 174, 180, 186, 192, 198, 204, 210
10: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210
14: 14, 28, 42, 56, 70, 84, 98, 112, 126, 140, 154, 168, 182, 196, 210
Second option - divide each option by the numbers to see if a whole number is the outcome.
30 / 6 = 5
30 / 10 = 3
30 / 14 = 2.14...
140 / 6 = 23.33...
210 / 6 = 35
210 / 10 = 21
210 / 14 = 15
Answer = C. 210
