[tex]\begin{gathered} 7+5r+3+5=1+7r \\ 15+5r=1+7r \\ 15-1=7r-5r \\ 14=2r \\ r=\frac{14}{2} \\ r=7 \end{gathered}[/tex][tex]\begin{gathered} 8n-7=7n-14 \\ 8n-7n=-14+7 \\ n=-7 \end{gathered}[/tex][tex]\begin{gathered} -4+6k+8=-4-7k \\ 4+6k=-4-7k \\ 4+4=-7k-6k \\ 8=-13k \\ k=-\frac{8}{13} \end{gathered}[/tex][tex]\begin{gathered} 4+7n=6n+2n \\ 4=8n-7n \\ n=4 \end{gathered}[/tex][tex]\begin{gathered} 15-7m=-5-2m \\ 15+5=-2m+7m \\ 20=5m \\ m=\frac{20}{5} \\ m=4 \end{gathered}[/tex]
