В: 1) 2/(5a) + 1/(6b) =; 2) 1/(7c) − 1/(5d) =; 3) 5/(8x) + 1/(12y) =; 4) 11/(12k) − 5/(18c) =; 5) a/(6x) + 4/(9xy) =; 6) 3/(20bc) − x/(15c) =; 7) 3/(ab) + 2/(ac) =; 8) 1/(xy) − 1/(xz) =; 9) 2/(ab) − 2/(cx) =; 10) 5/(abx) + z/(acy) =.

Приводим дроби к общему знаменателю, затем складываем или вычитаем числители.

1. 2/(5a) + 1/(6b) = 12b/(30ab) + 5a/(30ab) = (12b + 5a)/(30ab).
2. 1/(7c) − 1/(5d) = 5d/(35cd) − 7c/(35cd) = (5d − 7c)/(35cd).
3. 5/(8x) + 1/(12y) = 15y/(24xy) + 2x/(24xy) = (15y + 2x)/(24xy).
4. 11/(12k) − 5/(18c) = 33c/(36kc) − 10k/(36kc) = (33c − 10k)/(36kc).
5. a/(6x) + 4/(9xy) = 3ay/(18xy) + 8x/(18xy) = (3ay + 8x)/(18xy).
6. 3/(20bc) − x/(15c) = 9/(60bc) − 4bx/(60bc) = (9 − 4bx)/(60bc).
7. 3/(ab) + 2/(ac) = 3c/(abc) + 2b/(abc) = (3c + 2b)/(abc).
8. 1/(xy) − 1/(xz) = z/(xyz) − y/(xyz) = (z − y)/(xyz).
9. 2/(ab) − 2/(cx) = 2cx/(abcx) − 2ab/(abcx) = 2(cx − ab)/(abcx).
10. 5/(abx) + z/(acy) = 5cy/(abcxy) + bxz/(abcxy) = (5cy + bxz)/(abcxy).