Respuesta :

Answer:

15+x=-21

-15     -15

x=-36

-36 must be added into 15 to obtain -21

-Hope this helps

Answer:

x= -36 so -36 must be added to obtain 15 and -21

Step-by-step explanation:

15+x=-21

x+15=-21

subtract 15 from both sides 15 and -21

x= -36