Final answer:
Biola's initial amount of marbles, represented by Z, minus 6 marbles given away, equals Y, the remaining marbles. The simple equation is Z - 6 = Y.
Step-by-step explanation:
The simple equation representing the scenario where Biola had Z marbles and then gave away 6 can be written as:
Z - 6 = Y
where Z is the original number of marbles that Biola had, and Y represents the number of marbles Biola has after giving away 6. This equation shows the relationship between the initial amount of marbles and the amount left after some have been given away.