674. 7x+9 (2+x) = - 4x+3.

675. - x+4 (7-x) = - 7x+5.

676. X-3 (1-7x) = 2x+2.

677. - 9x-9 (4-x) = 3x+3.

674

7x+18+9x+4x-3=0

20x=-15

x=-0,75

675

-x+28-4x+7x-5=0

2x=-23

x=-11,5

676

x-3+21x-2x-2=0

20x=5

x=0,25

677

-9x-36+9x-3x-3=0

-3x=39

x=-13

678.

5x-6 (5+2x) = x-2

5x-30-12x-x+2=0

-8x=28

x=-3,5

679.

9x-2 (-1-x) = x-5

9x+2+2x-x+5=0

10x=-7

x=-0,7

680.

6x-8 (-7+9x) = - 2x-8

6x+56-72x+2x+8=0

-64x=-64

x=1