Question

-7-(0,3x-8)+3-(0,4x+5)=8

Answer 1

1)раскрываем скобки:
-7-0,3x+8+3-0,4x-5=8
2)решаем:
-0,7x=8+1
-0.7x=9
0.7x=-9
x=-9/0.7
x=-12.8

Answer 2

-7-(0,3х-8)+3-(0.4х+5)=8
-7-0.3х+8+3-0.4х-5=8
-1-0.7х=8
-0.7х=8-1
-0.7х=7
х=7:(-0.7)
х=-10

проверка: -7-(0.3х(-10)-8)+3-(0.4х(-10)+5)=8
-7+11+3+1=8
8=8