Answer:
[tex]\frac{1}{a} =\frac{1}{b} +\frac{1}{c} \\ \\\frac{1}{a} = \frac{1}{3} + \frac{1}{2/3} \\\\\frac{1}{a} = \frac{1}{3} + \frac{3}{2}\\\\\frac{1}{a} = \frac{11}{6}\\\\a = \frac{6}{11}[/tex]