Răspuns:
a = 27
Explicație pas cu pas:
5+[45×2+(5×4-135:a×3)-9×6]×6=251
[90+(20-135:a×3)-54]×6 = 251-5
[90+(20-135:a×3)-54]×6 = 246
90+(20-135:a×3)-54 = 246 : 6
90+(20-135:a×3)-54 = 41
90+(20-135:a×3) = 41 + 54
20 -135 : a × 3 = 95 - 90
20 -135 : a × 3 = 5
135 : a × 3 = 20 - 5
135 : a = 15 : 3
135 : a = 5
a = 135 : 5
a = 27
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