a) x : 2 + x : 3 + x : 4 + x : 5 = 15,4
x : ( 2 + 3 ) + x : ( 4 + 5 ) = 15,4
x : 5 + x : 9 = 15,4
x : ( 5 + 9 ) = 15,4
x : 14 = 15,4
x = 15,4 x 14
x = 215,6
\(x\div2+x\div3+x\div4+x\div5=15,4\)
\(\Leftrightarrow\frac{x}{2}+\frac{x}{3}+\frac{x}{4}+\frac{x}{5}=15,4\)
\(\Leftrightarrow x\left(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+\frac{1}{5}\right)=15,4\)
\(\Leftrightarrow x\left(\frac{30}{60}+\frac{20}{60}+\frac{15}{60}+\frac{12}{60}\right)=\frac{154}{10}\)
\(\Leftrightarrow\frac{77}{60}x=\frac{77}{5}\)
\(\Leftrightarrow x=\frac{77}{5}\div\frac{77}{60}\)
\(\Leftrightarrow x=12\)
\(\frac{202020}{323232}+\frac{348}{369}+\frac{1234}{2468}\)
\(=\frac{5}{8}+\frac{116}{123}+\frac{1}{2}\)
\(=\frac{5}{8}+\frac{116}{123}+\frac{4}{8}\)
\(=\frac{9}{8}+\frac{116}{123}\)
\(=\frac{1107}{984}+\frac{928}{984}\)
\(=\frac{2035}{984}\)