4x+40=6x-40 и ещё 6x-15=4x+5

4x+40=6x-40;                                      6x-15=4x+5;

4x-6x=-40-40;                                     6x-4x=15+5;

-2x=-80                                               2x=20;

x=-80:(-2)                                           x=20:2;

x=40.                                                  x=10.

Ответ:x=40.                                        Ответ:х=10.

1)6x-4x=40+40

    2x=80

    x=80/2

    x=40

2)6x-4x=5+15

    2x=20

    x=20/2

    x=10