[tex] \frac{1}{a} = \frac{1}{b} + \frac{1}{c} \\ \\ \frac{1}{12} = \frac{1}{b} + \frac{1}{22} \\ \\ \frac{1}{b} = \frac{1}{12} - \frac{1}{22} \\ \\ \frac{1}{b} = \frac{11}{132} - \frac{6}{132} \\ \\ \frac{1}{b} = \frac{11 - 6}{132} \\ \\ \frac{1}{b} = \frac{5}{132} \\ \\ 5b = 132 \\ \\ b = \frac{132}{5} \\ \\ b = 26.4 \\ \\ b = 26[/tex]
I hope I helped you^_^
