3,5 - 1 целая 1/2 умножить (1 целая 2/5 + 2/15)

3,5 - 1 1/2 * (1 2/5 + 2/15) = 7/2 - 3/2 * (7/5 + 2/15)
7/5 + 2/15 = (21+2) / 15 = 23/15
7/2 - 3/2 * 23/15
3/2 * 23/15 = 23/10
7/2 - 23/10 = (35-23) / 10 = 12/10 = 6/5 = 1 1/5 = 1,2