Дроби -3/20-7/30+2/40

-3/20-7/30+2/40= -6/120-280/120+6/120=-280/120=-2 1/3

[latex]- \frac{3}{20}- \frac{7}{30}+ \frac{2}{40}=- \frac{18}{120}- \frac{28}{120}+ \frac{6}{120}= \frac{-18-28+6}{120}= \frac{-40}{120}=- \frac{1}{3}[/latex]