3/7+4/21-13/14= bantu aku jawab yaa

3/7 = 18/42
4/21 = 8/42
13/14 = 39/42

= 3/7 + 4/21 - 13/4
= 18/42 + 8/42 - 39/42
= 26/42 - 39/42
= - 13/42

3/7 + 4/21 - 13/14 =
9/21 + 4/21 - 91/21 = -78/21 = 3 10/21