To find out after how many days the library will have enough people signed up to run the event, we need to consider the current number of sign-ups and how many more will be added each day.
Currently, there are 3 people signed up, and the library expects 2 more sign-ups each day.
Let \( d \) be the number of days after which we want to calculate the total sign-ups. The total number of people signed up after \( d \) days can be expressed as:
\[ 3 + 2d \]
The library needs at least 15 people to run the event, so we can set up the following inequality:
\[ 3 + 2d \geq 15 \]
This inequality can be solved to find the value of \( d \):
\[ 2d \geq 15 - 3 \] \[ 2d \geq 12 \] \[ d \geq 6 \]
Thus, the library will be sure it can run the event after 6 days.
The correct inequality that could be used to solve this problem is:
2d + 3 ≥ 15, where d is the number of days.