Final answer:
Carmen needs at least 19 more signatures to reach the required 100 for her petition.
Step-by-step explanation:
Carmen needs at least 100 signatures to submit a petition and currently has 81. To find the minimum number of additional signatures required for Carmen to submit the petition, we can subtract the number of signatures she already has from the total needed:
100 signatures needed - 81 signatures already obtained = 19 additional signatures required.
Therefore, Carmen needs to collect at least 19 more signatures to reach the minimum requirement of 100 signatures to submit her petition. This is a straightforward mathematical calculation often encountered in real-world scenarios, such as political campaigns or local ballot initiatives.