12 целых : 3 целых 3\8 - 1 целая 1\4 : 15\32 = заранее.

12 : 3 3/8 - 1 1/4 : 15/32 = 12/1 : 27/8 - 5/4 : 15/32 = 12 * 8 / 1*27 - 5 * 32 / 4 * 15 =
= 96/27 - 160/60 = 32/9 - 8/3 = 32/9 - 24/9 = 32 - 24 /9 = 8/9