Răspuns: x = 7
Explicație pas cu pas:
10 020 - 3 × { 56 - 2 × [18 + 3 × ( 6 + 3×x ) ] : 9 } = 9 918
3 × { 56 - 2 × [18 + 3 × ( 6 + 3×x ) ] : 9 } = 10 020 - 9 918
3 × { 56 - 2 × [18 + 3 × ( 6 + 3×x ) ] : 9 } = 102
56 - 2 × [18 + 3 × ( 6 + 3×x ) ] : 9 = 102 : 3
56 - 2 × [18 + 3 × ( 6 + 3×x ) ] : 9 = 34
2 × [18 + 3 × ( 6 + 3×x ) ] : 9 = 56 - 34
2 × [18 + 3 × ( 6 + 3×x ) ] : 9 = 22
2 × [18 + 3 × ( 6 + 3×x ) ] = 22 × 9
2 × [18 + 3 × ( 6 + 3×x ) ] = 198
18 + 3 × ( 6 + 3×x ) = 198 : 2
18 + 3 × ( 6 + 3×x ) = 99
3 × ( 6 + 3×x ) = 99 - 18
3 × ( 6 + 3×x ) = 81
6 + 3 × x = 81 : 3
6 + 3 × x = 27
3 × x = 27 - 6
3 × x = 21
x = 21 : 3
x = 7 → numărul, aflat prin metoda mersului invers
