Respuesta :

clz

Answer:

y=3

Step-by-step explanation:

12+3y=21

-12       -21    subtract 12 from both sides

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3y=9  

divide 3 from y and 9, so you can get y by itself

3y/3= y   9/3= 3

so y is equal to 3
when x=12, y = 3

y= 3 because

if you substitute 12 for x then you get
12+ 3y =21
you subtract 12 from each side and you get 3y =9 then you divide each side by 3 and you get y=3

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