2 020 - 10 : [ 4 - 4 : ( 8 - x × 2 ) ] + 21 = 2 036
2 020 - 10 : [ 4 - 4 : ( 8 - x × 2 ) ] = 2 036 - 21
2 020 - 10 : [ 4 - 4 : ( 8 - x × 2 ) ] = 2 015
10 : [ 4 - 4 : ( 8 - x × 2 ) ] = 2 020 - 2 015
10 : [ 4 - 4 : ( 8 - x × 2 ) ] = 5
4 - 4 : ( 8 - x × 2 ) = 10 : 5
4 - 4 : ( 8 - x × 2 ) = 2
4 : ( 8 - x × 2 ) = 4 - 2
4 : ( 8 - x × 2 ) = 2
8 - x × 2 = 4 : 2
8 - x × 2 = 2
x × 2 = 8 - 2
x × 2 = 6
x = 6 : 2
x = 3 → numarul, aflat prin metoda mersului invers
