Rusted off right before the canister it looks like. Right side of pic is the rear of car

 

Probably cannot be simply welded back together... you will likely have to cut the rusted parts out and replace whatever is removed with similar new parts.

 

The other side of that flange isn't far from failure.

Cheapest repair is probably cut away the rusted bits until you find solid material to weld to and then weld in a new section.

The correct repair would be to replace the exhaust from probably the cat back. If that section rotted away the rest of the system is probably not far behind.