Помогите решить дроби по действиям номер 871 и 869. Пж

Огромное спасибо

869)a)1) 3/4 + 1/6 = 9/12 + 2/12 = 11/122) 11/12 * 3 = 11/4 = 2 3/43) 5/6 - 1/2 = 5/6 - 3/6 = 2/6 = 1/34) 1/3 : 2/9 = 1/3 * 9/2 = 3/2= 1 1/25) 2 3/4 + 1 1/2 = 2 3/4 + 1 2/4 = 3 5/4 = 4 1/4----------------б)1) 1 1/5 + 2 3/10 = 1 2/10 + 2 3/10 = 3 5/10 = 3 1/22) 3 1/2 : 1/2 = 7/2 * 2 = 73) 6 3/4 - 2 2/3 = 6 9/12 - 2 8/12 = 4 1/124) 4 1/12 : 1 1/6 = 49/12 * 6/7 = 7/2 = 3 1/25) 7 + 3 1/2 = 10 1/2==================================871)a)1) 3/5 + 1/4 = 0,6+0,25 = 0,852) 17 : 0,85 =  203) 7/8 - 1/4 = 7/8 - 2/8 = 5/84) (4/5)² = 4/5 * 4/5 = 16/255) 5/8 * 16/25 = 2/5 = 0,46) 20 + 0,4 = 20,4б)1) 5/8 + 5/6 = 15/24 + 20/24 = 35/242) 70 : 35/24 = 70 * 24/35 = 483) 3 1/9 - 1/3 = 3 1/9 - 3/9 = 2 7/94) (3/10)² = 3/10 * 3/10 = 9/1005) 2 7/9 * 9/100 = 25/9 * 9/100 = 1/46) 48 + 1/4 = 48 + 0,25 = 48,25