7. а) \(\left(2x-3\frac{4}{15}\right)\cdot1,3=\frac{13}{25}\); б) \(2,25+0,5(11-3x)=4\frac{3}{8}\).

а)

\(3\frac{4}{15}=\frac{49}{15}\), \(1,3=\frac{13}{10}\).

\(\left(2x-\frac{49}{15}\right)\cdot\frac{13}{10}=\frac{13}{25}\)

\(2x-\frac{49}{15}=\frac{13}{25}\cdot\frac{10}{13}=\frac{2}{5}\)

\(2x=\frac{2}{5}+\frac{49}{15}=\frac{6}{15}+\frac{49}{15}=\frac{11}{3}\)

\(x=\frac{11}{6}\).

б)

\(2,25=\frac{9}{4}\), \(4\frac{3}{8}=\frac{35}{8}\).

\(\frac{9}{4}+0,5(11-3x)=\frac{35}{8}\)

\(0,5(11-3x)=\frac{35}{8}-\frac{18}{8}=\frac{17}{8}\)

\(11-3x=\frac{17}{4}\)

\(-3x=\frac{17}{4}-11=-\frac{27}{4}\)

\(x=\frac{9}{4}=2,25\).

Ответ: а) \(x=\frac{11}{6}\); б) \(x=2,25\).