Răspuns :
x+y+z=87
x=21
y=x+12
---------------
z=?
--------------
y=33→ z=33
verificare :33+33+21
66+21=87 R:z=33
x+y+z=87
x=21
y=x+12
---------------
z=?
--------------
y=33→ z=33
verificare :33+33+21
66+21=87 R:z=33