To do this without a calculator, the best method would be chunking.
Minus 36 from 936 in groups of ten until a smaller number is reached; record the number in each group.
936 - (10 x 36)
936 - 360 = 576
576 - (10 x 36)
576 - 360 = 216
216 - (5 x 36)
216 - 180 = 36
36 - (1 x 36)
36 - 36 = 0
Add up all the bold numbers
10 + 10 + 5 + 1 = 26