First, find the slope (y2-y1)/ (x2-x1) = (5-0)/(0-5)=-1
Then use the slope and any point to find your y-intercept --> 0=(-1)(5)+b, b=5
Then use it to create your equation in slope-intercept form y=-x+5
Since they are asking for standard form (Ax+By+C=0), rearrange to get
x+y-5=0
