I think your question seems to be ;
[tex]{\:\implies \quad \sf 3a-\dfrac23 +2a+\dfrac32 =a+\dfrac76}[/tex]
So I will be solving for that ;
[tex]{\:\implies \quad \sf 3a+2a+\left(\dfrac32 -\dfrac23\right)=a+\dfrac76}[/tex]
[tex]{\:\implies \quad \sf 5a+\left(\dfrac{9-4}{6}\right)=a+\dfrac76}[/tex]
[tex]{\:\implies \quad \sf 5a+\dfrac56 =a+\dfrac76}[/tex]
[tex]{\:\implies \quad \sf 5a-a=\dfrac76 -\dfrac56}[/tex]
[tex]{\:\implies \quad \sf 4a=\dfrac{7-5}{6}}[/tex]
[tex]{\:\implies \quad \sf 4a=\dfrac26}[/tex]
[tex]{\:\implies \quad \sf 4a=\dfrac13}[/tex]
[tex]{\:\implies \quad \sf a=\dfrac{1}{3\cdot 4}}[/tex]
[tex]{\:\implies \quad \bf \therefore \quad \underline{\underline{a=\dfrac{1}{12}}}}[/tex]
