(21/22-5/11)+(22/39-3/13)
21/22 - 5/11 =(21 × 1 - 5 × 2)/22 = 21/22 - 10/22 = 11/22 = 1/2 22/39 - 3/13 =(22 × 1 - 3 × 3)/39 = 22/39 - 9/39 = 13/39 = 1/3 1/2 + 1/3 =1 × 3 + 1 × 2)/6 = 3/6 + 2/6 = 5/6
(21/22-5/11)+(22/39-3/13)=(21/22-10/22)+(22/39-9/39)=11/22+13/39=1/2+1/3=(3+2)/6=5/6