Answer:
Expended form:

The number name is:
Twelve and three hundred seventy-five thousandths.
Explanation:
Consider the provided information.
Dimitri averaged 12.375 rebounds per game.
Here 1 is at tens place, 2 is at ones place, 3 is at tenths place, 7 is at hundredths place and 5 is at thousandths place.
The expanded form of the number is:
10+2+0.3+0.07+0.005
Or

The number name is:
Twelve and three hundred seventy-five thousandths.