Respuesta :

AL2006
9+x / 3x  =  5/6

If you look at it as a proportion, then you can "cross-multiply" it"

(9+x) · 6  =  3x · 5

54 + 6x  =  15x

Subtract 6x from each side:

54  =  9x

Divide each side by 9 :

6 = x