Answer: 126
Step-by-step explanation: You would just find the LCM (2, 3, 7) and get 42. But since you need a 3-digit number, list the multiples of 42, like so: 42, 84, 126, 168, 210...
As you can see, 126<em> </em>is the smallest 3-digit number that has 2, 3, and 7 among its prime factors.