\(c.6,7\times9,3+3,3\times9,3\)
\(=9,3\times\left(6,7+3,3\right)=9,3\times10=93\)
\(d.5,5\times-4,5\times4,7\)
\(=4,7\times\left(5,5-4,5\right)=4,7\times1=4,7\)
\(e.5,6\times4+5,6\times3+5,6\times2+5,6\)
\(=5,6\times\left(4+3+2+1\right)=5,6\times10=56\)