Answer :
[tex]6x-12+2x=3+8x-15 \\ \\ 8x-12=8x-12 \\ \\ 8x-8x=-12+12 \\ \\ \boxed{0=0}[/tex]
[tex]6x-12+2x=3+8x-15\\\\Add\ similar\ numbers:\\\\
8x-12=8x-12\\\\
0=0\\\\
If\ left\ side\ is\ equal\ to\ right\ side\ equation\ has\ infinitely\ many\\solutions.[/tex]