5 + (7 х-12) / 3=х+13

14 (2 х-3) - 5 (х+4) = 2 (3 х+5) + 5 х

(7x-12) / 3=x+13-5; (7x-12) / 3=x+8; (7x-12) / 3*3 = (x+8) * 3; 7x-12=3x+24; 7x-3x=24+12; 4x=36; x=36/4; x=9

14 (2 х-3) - 5 (х+4) = 2 (3 х+5) + 5 х; (28x-42) - (5x+20) = 6x+10+5x; 28x-42-5x-20=11x+10; 23x-62=11x+10; 23x-11x=10+62; 12x=72; x=72/12; x=6

1)

5+7x-12/3=x+13

3*5+3*7x+12/3=3x+3*13

15+7x-12=3x+39

3+7x=3x+39

7x-3x=39-3

4x=36

x=9