Respuesta :

Answer:

x=-9

Step-by-step explanation:

[tex]13-x=21\\\\12-x+x=21+x\\\\12+0=21+x\\\\21+x=12\\\\21-21+x=12-21\\\\0+x=-9\\\\x=-9[/tex]

Answer:

- 8

Step-by-step explanation:

13 - x = 21

-x = 8             Subtract 13 from both sides

x = -8             Divide both sides of -1 since x still has a negative.