Step-by-step explanation:
"At least x" means "that value x or more"
"At least 2" means "2 or more"
So Billy's plants grow 2 inches or more a month. The smallest increase possible is 2 inches.
We plot a closed circle at 2 on the number line. The closed circle tells us "include this value in the solution set". In contrast, the open circle says "exclude the endpoint from the solution set"
Then we shade to the right indicating all of the possible outcomes (growing 3 inches, growing 4 inches, etc.).