a)
[tex] - ( - 2k - 3) - ( - 7 + 5k - {k}^{2}) = 2k + 3 + 7 - 5k + {k}^{2} ={k}^{2} - 3k + 10[/tex]
b)
[tex] - (3 - 4x) + (x - 1) - (2x - 9) = - 3 + 4x + x - 1 - 2x + 9 = 3x + 5[/tex]
c)
[tex](12a + 13) - ( - 5 - a) = 12a + 13 + 5 + a = 13a + 18[/tex]
