Add. Simplify, if possible. \[ \begin{array}{c} 5 \frac{2}{3}+7 \frac{5}{9} \\ {[?] \frac{[]}{[]}} \end{array} \]

Step 1 ：5 + 7 = 12

Step 2 ：\frac{2}{3} + \frac{5}{9} = \frac{6}{9} + \frac{5}{9}

Step 3 ：\frac{6}{9} + \frac{5}{9} = \frac{11}{9} = \frac{2 \times 9 + 5}{3 \times 9} = \frac{23}{27}