\(\left(45,8-y\right)\times2,8=46,06\\ \rightarrow45,8-y=46,06:2,8\\ \rightarrow45,8-y=16,45\\ \rightarrow y=45,8-16,45\\ \rightarrow y=29,35\)

\(a,6:\dfrac{5}{2}-\dfrac{3}{10}=6\times\dfrac{5}{2}-\dfrac{3}{10}=\dfrac{12}{5}-\dfrac{3}{10}=\dfrac{24}{10}-\dfrac{3}{10}=\dfrac{21}{10}\)

\(b,\dfrac{4}{6}:\dfrac{4}{3}+5:\dfrac{4}{3}=\dfrac{4}{6}\times\dfrac{3}{4}+5\times\dfrac{3}{4}=\dfrac{2}{4}+\dfrac{15}{4}=\dfrac{17}{4}\)