1. Выполните действие: 1) 3/20 + 7/15; 2) 3 17/27 − 2 13/18; 3) 55/72 · 40/99; 4) 2 1/4 : 3 3/5; 5) −5 7/9 + (−3 4/9); 6) 14,6 + (−6,4); 7) 16,8 − (−2,6); 8) −4 2/7 · 1 2/5.

1. \(\frac{3}{20}+\frac{7}{15}=\frac{9}{60}+\frac{28}{60}=\frac{37}{60}\).
2. \(3\frac{17}{27}-2\frac{13}{18}=1+\frac{34}{54}-\frac{39}{54}=1-\frac{5}{54}=\frac{49}{54}\).
3. \(\frac{55}{72}\cdot\frac{40}{99}=\frac{5}{9}\cdot\frac{5}{9}=\frac{25}{81}\).
4. \(2\frac14:3\frac35=\frac94:\frac{18}{5}=\frac94\cdot\frac5{18}=\frac58\).
5. \( -5\frac79+(-3\frac49)=-(5\frac79+3\frac49)=-9\frac{11}{9}=-10\frac29\).
6. \(14,6+(-6,4)=14,6-6,4=8,2\).
7. \(16,8-(-2,6)=16,8+2,6=19,4\).
8. \(-4\frac27\cdot1\frac25=-\frac{30}{7}\cdot\frac75=-6\).

Ответ: 1) 37/60; 2) 49/54; 3) 25/81; 4) 5/8; 5) −10 2/9; 6) 8,2; 7) 19,4; 8) −6.