\(a,\frac{3}{4}+\frac{2}{7}+\frac{1}{4}+\frac{5}{7}+\frac{3}{5}\)
\(=\left(\frac{3}{4}+\frac{1}{4}\right)+\left(\frac{2}{7}+\frac{5}{7}\right)+\frac{3}{5}\)
\(=1+1+\frac{3}{5}\)
\(=2+\frac{3}{5}\)
\(=\frac{13}{5}\)
\(b,\frac{7}{3}.\frac{5}{7}.\frac{21}{5}=\frac{7.5.3.7}{3.7.5}=7\)
học tốt
a,\(\frac{3}{4}+\frac{2}{7}+\frac{1}{4}+\frac{5}{7}+\frac{3}{5}\)
\(=\left(\frac{3}{4}+\frac{1}{4}\right)+\left(\frac{2}{7}+\frac{5}{7}\right)+\frac{3}{5}\)
\(=1+1+\frac{3}{5}\)
\(=\frac{13}{5}\)
b,\(\frac{7}{3}\times\frac{5}{7}\times\frac{21}{5}=\frac{7\times5\times21}{3\times7\times5}=\frac{735}{105}=7\)