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2 ( 3 x + 4) - 5 ( 1 - 2 x) = 7 ( 2 x + 3) + 12
6 x + 8 - 5 + 10 x = 14 x + 21 + 12
16 x + 3 = 14 x + 33
16 x - 14 x = 33 - 3
2 x = 30
x = 15
( 2 x + 1) ( 5 - 6 x) = - 3 x ( 4 x - 1)
10 x - 12 x² + 5 - 6 x = - 12 x² + 3 x
- 12 x² + 4 x + 5 = - 12 x² + 3 x
- 12 x² + 12 x² + 4 x + 5 = 3 x
4 x + 5 = 3 x
4 x - 3 x = - 5
x = - 5