Respuesta :

3r/4+2r/1+r/2

3r/4+4x2r/4x1+r/2

3r/4+4x2r/4x1+r/2+2r/2x2

3r/4+8r/4x1+2r/2x2

3r+8r+2r/4

13r/4

13/4=r