a)
[tex][ - 9 + ( - 3) \times ( - 4)] \times [2 - ( - 6) \div ( + 3)] - ( + 12) = [/tex]
[tex][ - 9 + ( -12)] \times [2 - ( - 2)] - 12 = [/tex]
[tex]( - 9 - 12) \times (2 + 2) - 12 = [/tex]
[tex]( - 21) \times 4 - 12 = [/tex]
[tex] - 84 - 12 = [/tex]
[tex] = 96[/tex]
b)
[tex] { [ {( - 19)}^{3} ] }^{4} \div ( - 1 9){}^{11} + {2}^{17} \div { [ {( -2)}^{2} ] }^{8} = [/tex]
[tex] { {( - 19)}^{12} }^{} \div ( - 1 9){}^{11} + {2}^{17} \div { {( -2)}^{16} }^{} = [/tex]
[tex] {( - 19)}^{1} + ( - 2) {}^{1} = - 19 - 2 = - 21[/tex]
