11/18 + 13/27 =

\[\frac{11}{18} + \frac{13}{27} = \frac{11 \times 3}{18 \times 3} + \frac{13 \times 2}{27 \times 2} = \frac{33}{54} + \frac{26}{54} = \frac{33+26}{54} = \frac{59}{54} = 1\frac{5}{54}\]