5).(2x + 1)/(12x²y) + (2 – 3y)/(18xy²) = (6xy + 3y + 4x – 6xy)/(36x²y²) = (4x + 3y)/(36x²y²);

6). (a + 4)/a – (a + 6)/(a + 2) = (a² + 6a + 24- a² - 6a)/[a (a + 2)] = 24/[a (a + 2)];