72.
[tex] {2009}^{2009} \div {2009}^{2007} \times {2009}^{2003} \div {2009}^{2005} = {2009}^{2009 - 2007 + 2003 - 2005} = {2009}^{0} = 1[/tex]
73.
[tex]x + x + 1 + x + 2 = 0[/tex]
[tex]3x + 3= 0[/tex]
[tex]3x = - 3[/tex]
[tex]x = - 1[/tex]
76.
[tex]14 \times (x + 1) = 15 \times x[/tex]
[tex]14x + 14 = 15x[/tex]
[tex]x = 14[/tex]
