Example 1
Over the years, several visitors to the Scottish Highlands have spotted the Loch Ness Monster.
In this example, several is an indefinite adjective that modifies the noun visitors because the specific number of people that have claimed to see Nessie isn't given.
P.S. The most famous evidence of the Loch Ness Monster, "The Surgeon's Photograph," was revealed to be a hoax in 1975. Most analysts agree that the picture is actually of a toy submarine with a sculpted head attached, which all analysts agree is significantly less terrifying than a giant lake monster.
Example 2
Do we have enough gas to get to Fresno?
Here, enough is an indefinite adjective that modifies the noun gas. Why anybody would be in a rush to get to Fresno is beyond us.
Just joshin' you, Fresno. We love you, and we love your raisins.
Example 3
If Isaiah pushes the table a few inches to the left, he can cover the hole he just accidentally burned in the rug.
In this sentence, the indefinite adjective few refers to the unspecified number of inches that Isaiah needs to nudge the table in order to prevent his mother from killing him when she gets home from work.