can you simplify x> -1,y>3,x+y<8

(x > -1)+(y>3)=x+y>2

so

2 < x+y < 8

and that's all you can simplify it

I'm not sure, but I think the questioner might want to define a "feasible" region here...

It's given by the area inside triangle GHD on the graph...none of the sides are included in the feasible region.......

If this is not the intent........sorry !!!

The enclosed region shows where they are all true at the same time.

This is the INTERSECTION of the regions.