Tính:

----- Nội dung ảnh -----
Bài 4: Tính:

a) \( \frac{2}{9} - \frac{1}{3} + \frac{5}{27} \)

b) \( \frac{3}{4} + \frac{11}{15} - 1 \)

c) \( \frac{3}{8} + \frac{6}{18} + \frac{9}{27} + \frac{2}{16} \)

d) \( \frac{13}{26} + \frac{1}{3} - \frac{1}{2} + \frac{7}{21} \)