[tex]\mleft(6r+7\mright)+\mleft(13+7r\mright)=13r+20[/tex][tex]\begin{gathered} (13-\frac{3}{2}r)-(1-r) \\ =13-\frac{3}{2}r-1+r \\ =12-\frac{3}{2}r+r \\ =12-\frac{1}{2}r \end{gathered}[/tex][tex]\begin{gathered} (-8-r)+(2r-4) \\ =-8-r+2r-4 \\ =-12+r \end{gathered}[/tex][tex]\begin{gathered} (7r-\frac{3}{2})-(\frac{2}{3}+6r) \\ =7r-\frac{3}{2}-\frac{2}{3}-6r \\ =r-\frac{13}{6} \end{gathered}[/tex]
