a) Rút gọn:\(\frac{5.6+5.7}{5.8+20}=\frac{5.6+5.7}{5.8+5.4}=\frac{5.\left(6+7\right)}{5.\left(8+4\right)}=\frac{5.13}{5.12}=\frac{13}{12}\)
\(\frac{8.9-4.15}{12.7-180}=\frac{2.4.3^2-4.3.5}{12.7-12.15}=\frac{\left(2.3\right).\left(4.3\right)-\left(4.3\right).5}{12.\left(7-15\right)}=\frac{6.12-12.5}{12.\left(-8\right)}=\frac{12.\left(6-5\right)}{-8.12}\)
=\(\frac{12.1}{-8.12}=-\frac{1}{8}\)
Quy đồng: MC(mẫu chung): 24
Ta có: \(\frac{13}{12}=\frac{13.2}{12.2}=\frac{26}{24}\), \(-\frac{1}{8}=-\frac{3}{8.3}=-\frac{3}{24}\)