a) (2x - 7)/4x + (3 + 4x)/4x
= (2x - 7 + 3 + 4x)/4x
= (6x - 4)/4x
= (3x - 2)/2x
b) (9x - 5)/(x² + x) + (10 - 4x)/(x² + x)
= (9x - 5 + 10 - 4x)/[x(x + 1)]
= (5x + 5)/[x(x + 1)]
= 5(x + 1)/[x(x + 1)]
= 5/x
c) (3x - 9)/(x - 1) : (x² - 9)/(x² - 2x + 1)
= 3(x - 3)/(x - 1) . (x - 1)²/[(x - 3)(x + 3)
= 3(x - 1)/(x + 3)