Salut!
Răspuns: 9; 11
Notam cu x primul melc si cu y al doilea melc
1. Metoda pentru clasele I - IV
x + y = 20
y = x + 2
x + x + 2 = 20
2x = 20 - 2
2x = 18
x = 18 : 2
x = 9
y = 9 + 2
y = 11
Verificare: 9 + 11 = 20
2. Metoda pentru clasele gimnaziale ( V - VIII )
[tex]\bf\left \{ {{x+y=20} \atop {y=x+2}} \right. <=>\left \{ {{x + x+2=20} \atop {y=x+2}} \right.<=>\left \{ {{2x=20-2} \atop {y=x+2}} \right. <=> \left \{ {{2x=20-2} \atop {y=x+2}} \right.<=>\left \{ {{2x=18} \atop {y=x+2}} \right. <=>\left \{ {{x=18:2} \atop {y=x+2}} \right. <=>\left \{ {{x=9} \atop {y=9+2}} \right. <=>\left \{ {{x=9} \atop {y=11}} \right. => S(9;11)[/tex]
