OPLOSSING

[12 - (8 - 4)] - [-21 + (17 + 2) - (-5 + 3) + 6]

= [12 - 8 + 4] - [-21 + 17 + 2 + 5 - 3 + 6]

= 12 - 8 + 4 + 21 - 17 - 2 - 5 + 3 - 6

= 2

terug