0/100 or Zero.
9/10 minus 1/10 is 4/5
9/10 minus 7/8 is 1/40
9/10 minus 3/5 is 3/10
9/10 − 4/5 = 1/10
3/5 − 9/10 = -3/10
9/10 - 4/5 = 9/10 - 8/10 = 1/10
9/10 - 7/10 = 2/10 = 1/5
9/10 − 1/3 = 17/30
9/10 - 1/2 = 9/10 - 5/10 = 4/10 = 2/5
9/10 - 3/10 = 6/10 or as 3/5 in its lowest terms
9/10 − 2/3 = 7/30
9/10 - 2/5 = 9/10 * 4/10 = 5/10 = 1/2 or 0.5