50 номер помогите решить плиизз

А) $\frac{1}{ \frac{1}{2} - \frac{1}{3} } = \frac{1}{ \frac{3}{6} - \frac{2}{6} }= \frac{1}{ \frac{1}{6}}=6$
$\frac{6-6}{6+6} = \frac{0}{12} =0$

б) $1+ \frac{1}{3} = \frac{3}{3} + \frac{1}{3}=\frac{4}{3}$
$\frac{2}{ \frac{4}{3} } =2* \frac{3}{4} =\frac{3}{2}$
$1+\frac{3}{2}=\frac{2}{2}+\frac{3}{2}=\frac{5}{2}$
$1:\frac{5}{2}=1*\frac{2}{5}=\frac{2}{5}$
$2+\frac{2}{5}=2\frac{2}{5}$

в)1+ 1/3=3/3 + 1/3=4/3
1: 4/3=3/4
1+ 3/4=4/4 + 3/4=7/4
1: 7/4=4/7
1 + 4/7=7/7 + 4/7=11/7
1: 11/7=7/11