In short, y=-x+3,
We know that our slope is -1, this means that for every time we move to the right 1, we will go down 1.
We can model this in the form, y=mx+b, where m is our slope and b is our y-intercept, where our line will intersect the y-axis as the name suggests.
So, we can complete the part of, y=-1x+b, but we still don’t know our y-intercept.
We can find this by plugging in any point on our line and solving this as a simple one-step equation.
Let’s use the point that we were given, (-2,5). So we can plug in x/y like so,
5=-1•-2+b
5=2+b
3=b
So, now we can plug in everything, y=-1x+3, or y=-x+3.
Hope this helps!