Сложение смешанных дробей. 2 3/4+1 2/3 8 3/5+1 9/10 7/20 + 8 3/4 3 4/5+ 1 1/3 12 5/6+ 4/5

2 3/4+1 2/3=11/4 + 5/3 (11 × 3+5 × 4)/12 = 33 /12 +20/12 = 53/12 = 4 5/12
8 3/5+1 9/10=43/5  +  19/10  =(43 × 2  +  19 × 1)/10 = 86/10  +  19/10 =  105/10 = 21/2 = 10 1/2
7/20 + 8 3/4=7/20  +  35/4 =(7 × 1  +  35 × 5)/20 = 7/20  +  175/20 =  182/20 = 91/10 = 9 1/10
3 4/5+ 1 1/3= 19/5  +  4/3 =(19 × 3  +  4 × 5)/15 = 57/15  +  20/15 =  77/15 = 5 2/15
12 5/6+ 4/5=77/6  +  4/5 =(77 × 5  +  4 × 6)/30 = 385/30  +  24/30 =  409/30 = 13 19/30