**Answer:**

The greatest common factor of 36 and 54 is **18.**

**Step-by-step explanation:**

To solve this problem, first, you have to find the greatest common factor (GCF) of 36 and 54.

Factors of 36:

1, 2, 3, 4, 6, 9, 12,** 18, **and 36.

Factors of 54:

1, 2, 3, 6, 9,** 18,** 27, and 54.

Therefore, the greatest common factor of 36 and 54 is **18.**