125. Решите уравнения: a) 7x-3(x+4)=22-6x; б) 8x-9(3-2x)=10x-11; в) -5x+3(x-7)=4x-21; г) -9x+2=7+5(3-x).

Решение:

1. \( 7x - 3(x + 4) = 22 - 6x \)

\( 7x - 3x - 12 = 22 - 6x \)
\( 4x - 12 = 22 - 6x \)
\( 4x + 6x = 22 + 12 \)
\( 10x = 34 \)
\( x = 3.4 \)
2. \( 8x - 9(3 - 2x) = 10x - 11 \)

\( 8x - 27 + 18x = 10x - 11 \)
\( 26x - 27 = 10x - 11 \)
\( 26x - 10x = 27 - 11 \)
\( 16x = 16 \)
\( x = 1 \)
3. \( -5x + 3(x - 7) = 4x - 21 \)

\( -5x + 3x - 21 = 4x - 21 \)
\( -2x - 21 = 4x - 21 \)
\( -2x - 4x = 21 - 21 \)
\( -6x = 0 \)
\( x = 0 \)
4. \( -9x + 2 = 7 + 5(3 - x) \)

\( -9x + 2 = 7 + 15 - 5x \)
\( -9x + 2 = 22 - 5x \)
\( -9x + 5x = 22 - 2 \)
\( -4x = 20 \)
\( x = -5 \)

Ответ: a) \( x = 3.4 \); б) \( x = 1 \); в) \( x = 0 \); г) \( x = -5 \).