Răspuns
Explicație pas cu pas:
128 : 16 + 76 - 4 x [ ( 20 + 4 x a ) : 5] : 2 = 68
8 + 76 - 4 × [ ( 20 + 4 × a ) : 5 ] : 2 = 68
84 - 4 × [ ( 20 + 4 × a ) : 5 ] : 2 = 68
4 × [ ( 20 + 4 × a ) : 5 ] : 2 = 84 - 68
4 × [ ( 20 + 4 × a ) : 5 ] : 2 = 16
( 20 + 4 × a ) : 5 = 16 × 2 : 4 → aplic metoda mersului invers
( 20 + 4 × a ) : 5 = 32 : 4
( 20 + 4 × a ) : 5 = 8
20 + 4 × a = 8 × 5
20 + 4 × a = 40
4 × a = 40 - 20
4 × a = 20
a = 20 : 4
a = 5 → numarul
