Question 55127
The general method to solve such problems is as below.
Suppose the points are (x1,y1) and (x2,y2).
Then the reqd. equation is {{{(y - y1)/(y2 - y1)=(x - x1)/(x2 - x1)}}}.

Here x1 =0, x2 = 5, y1 = 7, y2 = 2.
So the equation is {{{(y - 7)/(2 - 7)=(x - 0)/(5 - 0)}}}
or {{{(y - 7)/( - 5)=x/5}}}
or {{{y - 7=-x}}}
or {{{x+y=7}}}