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