6 вариант. Вычислите: 1) 1/3 + 1/5; 2) 6/7 − 1/3; 3) 1/2 · 7/10; 4) 3/4 : 1/8; 5) 1 3/7 + 1 5/6; 6) 2 1/4 − 2/3; 7) 1 1/2 · 2 4/5; 8) 4 1/6 : 2 2/5; 9) 1/6 + 1; 10) 3 − 2/3; 11) 4 · 2/8; 12) 5/8 : 5.

1. \(\frac13+\frac15=\frac5{15}+\frac3{15}=\frac8{15}\).
2. \(\frac67-\frac13=\frac{18}{21}-\frac7{21}=\frac{11}{21}\).
3. \(\frac12\cdot\frac7{10}=\frac7{20}\).
4. \(\frac34:\frac18=\frac34\cdot8=6\).
5. \(1\frac37+1\frac56=\frac{10}{7}+\frac{11}{6}=\frac{60}{42}+\frac{77}{42}=\frac{137}{42}=3\frac{11}{42}\).
6. \(2\frac14-\frac23=\frac94-\frac23=\frac{27}{12}-\frac8{12}=\frac{19}{12}=1\frac7{12}\).
7. \(1\frac12\cdot2\frac45=\frac32\cdot\frac{14}{5}=\frac{21}{5}=4\frac15\).
8. \(4\frac16:2\frac25=\frac{25}{6}:\frac{12}{5}=\frac{25}{6}\cdot\frac5{12}=\frac{125}{72}=1\frac{53}{72}\).
9. \(\frac16+1=1\frac16\).
10. \(3-\frac23=2\frac13\).
11. \(4\cdot\frac28=1\).
12. \(\frac58:5=\frac58\cdot\frac15=\frac18\).

Ответ: 1) 8/15; 2) 11/21; 3) 7/20; 4) 6; 5) 3 11/42; 6) 1 7/12; 7) 4 1/5; 8) 1 53/72; 9) 1 1/6; 10) 2 1/3; 11) 1; 12) 1/8.