[tex]3x(m - 2) - 2mx + 9 = 5m + 56[/tex]
[tex]3 \times ( - 2)(m - 2) - 2m \times ( - 2) + 9 = 5m + 56[/tex]
[tex] - 6(m - 2) + 4m + 9 = 5m + 56[/tex]
[tex] - 6m + 12 + 4m + 9 = 5m + 56[/tex]
[tex] - 6m + 4m - 5m = 56 - 12 - 9[/tex]
[tex] - 7m = 35 \: | \div ( - 7)[/tex]
[tex]m = - 5[/tex]