Răspuns :
x:z=5=>x=5z
x-z=648=>x=648+z
5z=648+z
5z-z=648
4z=648=>z=648:4=162
x=648+162=810
x-z=648=>x=648+z
5z=648+z
5z-z=648
4z=648=>z=648:4=162
x=648+162=810
x:z=5
z-x=648
x=zx5
x=5z ⇒inlocuim pe x in z-x=648
z-5z=648
4z=648
z=648:4
z=162
x=5x162
x=810
Verificare : 810:162=5
z-x=648
x=zx5
x=5z ⇒inlocuim pe x in z-x=648
z-5z=648
4z=648
z=648:4
z=162
x=5x162
x=810
Verificare : 810:162=5