Answer:
7) y=3-x
9) y=x-3
Step-by-step explanation:
I'm going to assume that perhaps you're funding the notation here a bit strange but in question 7, x+y=3 is the same as saying y=3-x. You get this easily by subtractin x from both sides x+y-x=3-x => y=3-x.
Similarly in question 9, x-y=3 you add y to both sides and then subtract 3 from both sides. x-y+y-3=3+y-3 => x-3=y or y=x-3
You can now draw these lines into the graphs.
