Division as a subtraction
A division can be done as a succesive subtraction. For example, 12 / 3 can be divided by subtracting 3 as needed:
12 - 3 = 9
9 - 3 = 6
6 - 3 = 3
3 - 3 = 0
We cannot subtract anymore, thus we have reached the final result:
12/3 = 4 (the number of subtractions done) and the remainder is zero (the last result).
We are given the sequence:
18 - 6 = 12
12 - 6 = 6
6 - 6 = 0
This corresponds to the division 18/6 = 3
Correct choice: D