a) \(x:\left[\left(1800+600\right):30\right]=560:1515+35\)
\(x:\left[\left(1800+600\right):30\right]=\dfrac{112}{303}+35\)
\(x:\left[\left(1800+600\right):30\right]=\dfrac{10717}{303}\)
\(x:\left[2400:30\right]=\dfrac{10717}{303}\)
\(x:80=\dfrac{10717}{303}\)
\(x=\dfrac{10717}{303}.80\)
\(x=\dfrac{857360}{303}\)