a/ \(-\frac{81}{504}=-\frac{9}{56};-\frac{10101}{101010}=\frac{-1}{10}\)
b/ \(\frac{72\cdot5+72\cdot3}{144\cdot2+144\cdot6}=\frac{72\left(5+3\right)}{144\left(2+6\right)}=\frac{8}{2\cdot8}=\frac{1}{2}\)
\(\frac{-81}{504}=-\frac{81:9}{504:9}=-\frac{9}{56}\)
\(\frac{-10101}{101010}=\frac{-10101:10101}{101010:10101}=\frac{-1}{10}\)
\(\frac{72.5+72.3}{144.2+144.6}=\frac{72.\left(5+3\right)}{144\left(2+6\right)}=\frac{72.8}{144.8}=\frac{72.8}{72.2.8}=\frac{1}{2}\)