a,\(20*3246*5=100*3246\)

\(=324600\)

b,+346*47\(346*53+346*47=346*\left(53+47\right)\)

\(=346*100\)

\(=34600\)

a,\(\frac{7}{24}+\frac{13}{6}=\frac{7}{24}+\frac{52}{24}=\underset{24}{\overset{7+52}{\xrightarrow{}}}=\frac{59}{24}\) b,\(\frac{12}{49}-\frac17^{}=\frac{12}{49}-\frac{7}{49}=\underset{49}{\overset{12-7}{\xrightarrow{}}}=\frac{5}{49}\)

c,\(\frac58*\frac{24}{25}=\underset{8*25}{\overset{5*24}{\xrightarrow{}}}=\frac{200}{120}=\frac35\) d,\(\frac{38}{21}:\frac{19}{3}=\frac{38}{21}*\frac{3}{19}=\underset{21*19}{\overset{38*3}{\xrightarrow{}}}=\frac{114}{399}\)

a, 2228655

b, 13265