6+[15-(8:a×7+7)]×5=8: (1×4)+3×3

Răspuns :

6+[15-(8:a×7+7)]×5=8:4+9
6+[15-(8:a×7+7)]×5=11
[15-(8:a×7+7)]×5=5
15-(8:a×7+7)=1
8:a×7+7=15-1
8:a×7+7=14
8:a×7=7
8:a=1
a=8:1
a=8