Răspuns:
Explicație pas cu pas:
3 + 3 × {3 + 3 × [ 3 + 3 × ( 3 - 3 : a ) ] } = 3 × 31
3 + 3 × {3 + 3 × [ 3 + 3 × ( 3 - 3 : a ) ] } = 93
3 × {3 + 3 × [ 3 + 3 × ( 3 - 3 : a ) ] } = 93 - 3
3 × {3 + 3 × [ 3 + 3 × ( 3 - 3 : a ) ] } = 90
3 + 3 × [ 3 + 3 × ( 3 - 3 : a ) ] = 90 : 3
3 × [ 3 + 3 × ( 3 - 3 : a ) ] = 30 - 3
3 + 3 × ( 3 - 3 : a ) = 27 : 3
3 × ( 3 - 3 : a ) = 9 - 3
3 × ( 3 - 3 : a ) = 6
3 - 3 : a = 6 : 3
3 - 3 : a = 2
3 : a = 3 - 2
3 : a = 1
a = 3 : 1
a = 3 → numarul, aflat prin metoda mersului invers
