a) \(\frac{15}{50}+20\%+\frac{5}{100}+0,45\)
\(=\frac{3}{10}+\frac{1}{5}+\frac{1}{50}+\frac{9}{20}\)
\(=\frac{97}{100}\)
b) \(\frac{3}{6}\times\frac{8}{12}\times\frac{15}{20}\times\frac{24}{30}\times\frac{35}{42}\times\frac{48}{56}\times\frac{65}{72}\times\frac{80}{90}\)
\(=(\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\times\frac{5}{6}\times\frac{6}{7})\times\frac{65}{72}\times\frac{8}{9}\)
\(=\frac{1}{7}\times\frac{65}{72}\times\frac{8}{9}\)
\(=\frac{65}{567}\)