Ответ:

  1. \(\frac{5}{8}-\frac{4}{5}=\frac{25-32}{40}=-\frac{7}{40}\).
  2. \(\frac{1}{\frac{1}{18}-\frac{1}{21}}=\frac{1}{\frac{1}{126}}=126\).
  3. \(0{,}2:(1-\frac{1}{3})=0{,}2:\frac{2}{3}=0{,}3\).
  4. \((1{,}7+3{,}8):2{,}2=5{,}5:2{,}2=2{,}5\).
  5. \(21:(0{,}6\cdot2{,}8)=21:1{,}68=12{,}5\).
  6. \(\frac{(2\cdot3)^5}{2^4\cdot3^3}=2^{5-4}\cdot3^{5-3}=18\).
  7. \(\frac{15^8}{3^6\cdot5^7}=3^2\cdot5=45\).
  8. \(2^5:4=32:4=8\).
  9. \(5^{-3-9-(-14)}=5^2=25\).
  10. \(2^{-9+14}=2^5=32\).
  11. \((\frac{17}{26}+\frac{22}{26})\cdot\frac{17}{6}=\frac{3}{2}\cdot\frac{17}{6}=\frac{17}{4}\).
  12. \((\frac{5}{6}+\frac{1}{10})\cdot24=\frac{14}{15}\cdot24=\frac{112}{5}=22{,}4\).
  13. \(5{,}4\cdot1{,}9-2{,}15=10{,}26-2{,}15=8{,}11\).
  14. \(18\cdot\frac{1}{81}-\frac{20}{9}=\frac{2}{9}-\frac{20}{9}=-2\).
  15. \(-\frac{7}{18}\cdot0{,}9+3=-0{,}35+3=2{,}65\).
  16. \(0{,}6\cdot(-1000)+50=-550\).
  17. \(0{,}4\cdot(-216)+0{,}7\cdot36+49=-86{,}4+25{,}2+49=-12{,}2\).
  18. \(0{,}4+0{,}09+0{,}0001=0{,}4901\).