Answer:
14 rows.
Explanation:
It could be any amount, but there is a clear pattern that follows "-3". Starting from 51 and ending at 12, let's subtract by 3.
51, 48, 45, 42, 39, 36, 33, 30, 27, 24, 21, 18, 15, and 12.
There are 14 numbers; therefore, there are 14 rows.