We can see if the first two options are correct. The first one is eliminated because when x is 2, y is 5 and there is not a different of 5, only 3. This could make you think that the second option is the right answer, but when x is 1, y is 6 and the difference is 5, not 3.
The third choice we could try out.
6=-(1)+7
5=-(2)+7
4=-(3)+7
3=-(4)+7
Let's look at the graph also. The coordinates are on the line.
So the third option, y=-x+7