26+(-83);-43+53;-4.254+6.44;-6.7+5.9; 5/12+(-7/9);-11//42+5/28;-5/7+1;2,9/40+2,4/15

$26+(-83)=26-83=-57$

$-43+53=10$

$-4.254+6.44=2,186$

$-6.7+5.9=-0,8$

$\frac{5}{12}+(-\frac{7}{9})=\frac{5}{12}-\frac{7}{9}=\frac{15}{36}-\frac{28}{36}=-\frac{13}{36}$

$-\frac{11}{42}+\frac{5}{28}=-\frac{22}{84}+\frac{15}{84}=-\frac{7}{84}=-\frac{1}{12}$

$-\frac{5}{7}+1=-\frac{5}{7}+\frac{7}{7}=\frac{2}{7}$

$\frac{2,9}{40}+\frac{2,4}{15}=\frac{8,7}{120}+\frac{19,2}{120}=\frac{27,9}{120}=0,2325$