Respuesta :

gustanika
K = 4r - 7s
or I flip the side, so r will be on the left side
4r - 7s = K

move 7s to the other side, it becomes plus
4r - 7s = K
4r = K + 7s

move 4 to the other side, it becomes a divisor
4r = K + 7s
  r = [tex]\boxed{\cfrac{K+7s}{4}}[/tex]