1) 0,5 : 1,25 =0,4
2)1 2/5 : 1 4/7 = 7/5 : 11/7 = 7/5 * 7/11 = 49/55
3)0,4 + 49/55 = 4/10 + 49/55 =2/5 + 49/55 = (2 × 11 + 49 × 1)/55 = (22 + 49)/55 = 71/55 = 1 16/55
4)1 16/55 - 3/11 =71/55 - 3/11 =(71 × 1 - 3 × 5)/55 = (71 - 15)/55 = 56/55 = 1 1/55
5) 1 1/55 * 11 =56/55 * 11 = 56/5 = 11 1/5
ответ 11 1/5