12) 4 3/4 - 2 1/5 = (4 × 4 + 3)/4 - (2 × 5 + 1)/5 = (16 + 3)/4 - (10 + 1)/5 = 19/4 - 11/5 = (19 × 5)/(4 × 5) - (11 × 4)/(5 × 4) = 95/20 - 44/20 = (95 - 44)/20 = 51/20 = 2 11/20
Ответ: 2 11/20