What is the error on the subject-verb agreement?

Modern calculators, which can compute sums almost instantaneously, derives from abacuses, hand operated devices with beads that slide along rods.

Ur subject " calculators " is plural

ur verb " derives " is a singular verb ... it needs to be plural because ur subject is plural.

The correct way to write this would be:

Modern calculators, which can compute sums almost instantaneously, derive from abacuses, hand operated devices with beads that slide along rods.