Răspuns:
a-numarul necunoscut
[(a×4-300)×3-900]×2-300=900
[(a×4-300)×3-900]×2=900+300
[(a×4-300)×3-900]×2=1200
[(a×4-300)×3-900]=1200:2
(a×4-300)×3-900=600
(a×4-300)×3=600+900
(a×4-300)×3=1500
(a×4-300)=1500:3
a×4-300=500
a×4=500+300
a×4=800
a=800:4
a=200
200 este numărul
