r = 4 + 7x -sx
7x - sx = r - 4
x (7 -s) = r - 4
x = r -4 / 7 - s
if we know the value of s and r, we can find the value of x.
there is another way to solve this equation:
r = 4 + 7x - sx
7x - sx = r - 4
7x - sx - (r - 4) = 0
if we put 7x - sx in plce of r - 4, we get
7x - sx - (7x - sx) = 0
7x - sx -7x +sx = 0
Now 7x- 7x = 0 and sx - sx = 0
So all the terms gives the answer 0
the solution o this equation could not be determined.