18 11/12-4 5/9-5 1/6+4 1/4

$18\frac{11}{12}-4\frac{5}{9}-5\frac{1}{6}+4\frac{1}{4}=13\frac{4}{9}$

1) $18\frac{11}{12}-4\frac{5}{9}=\frac{227}{12}-\frac{41}{9}=\frac{681-164}{36}=\frac{517}{36}=14\frac{13}{36}$

2) $14\frac{13}{36}-5\frac{1}{6}=\frac{517}{36}-\frac{31}{6}=\frac{517-186}{36}=\frac{331}{36}=9\frac{7}{36}$

3) $9\frac{7}{36}+4\frac{1}{4}=\frac{331}{36}+\frac{17}{4}=\frac{331+153}{36}=\frac{484}{36}=\frac{121}{9}=13\frac{4}{9}$