1) \( \frac{7}{27} + \frac{12}{27} - \frac{13}{27} = \frac{19}{27} - \frac{13}{27} = \frac{6}{27} = \frac{2}{9} \)
2) \( 4 \frac{16}{32} + 3 \frac{5}{32} = 7 \frac{21}{32} \)
3) \( 1 - \frac{24}{36} = 1 - \frac{2}{3} = \frac{3}{3} - \frac{2}{3} = \frac{1}{3} \)
4) \( 7 \frac{1}{26} - 2 \frac{21}{26} = 6 \frac{27}{26} - 2 \frac{21}{26} = 4 \frac{6}{26} = 4 \frac{3}{13} \)