a) 0,12 - 1,375

1. Convert decimals to fractions: 0.12 = 12/100 = 3/25, 1.375 = 1375/1000 = 11/8.
2. Subtract the fractions: 3/25 - 11/8 = (24 - 275) / 200 = -251/200.
3. Convert back to decimal: -251/200 = -1.255.