linear equation, can't figure out formula?

Question

9x+3y=12. first solve for y, then solve for x. I cannot figure out formula.

they are two do different problems. First solve for y, then solve x for the same original problem.

they are two different problems. First solve for y, then solve x for the same original problem.

this is the answer in the back of the book for y ----- y = 4 - 3x----

y = 4 - 3x

sue has it right only the numbers need to be switched

thank you guys

Answer 1

Solve for y:

9x+3y=12

Subtract 9x

3y = -9x + 12

Divide by 3

y = -3x + 4

(this is equivalent to y = 4 - 3x)

Solve for x:

9x+3y=12

Subtract 3y

9x = -3y + 12

Divide by 9

x = -3/9y + 12/9

Simplify

x = -1/3x + 4/3

Answer 2

You need to isolate x and y in turn by performing the same operations on both sides of the equals sign.

9x + 3y -3y = 12 - 3y
9x = 12 - 3y
x = (12-3y)/9

3y + 9x - 9x = 12 - 9x
3y = 12 - 9x
y = (12 - 9x )/ 3

Answer 3

I hope that you don`t mind me saying that this is a very vague question. It would be a good idea for you to post a few specific questions on this site . Answerers could then give you an insight into methods of solution.

Answer 4

here how you do divide all by 3 and you get 3x+y=4then when x=0 y is 4 and when y=0 then x is 4 then (4,4/3)

Answer 5

9x+3y=12
3(3x+y)=12
3x+y=4
y=4-3x and x=(4-y)/3
When x=0 then y=4
when y=0 then x=4/3
(0,4) and (4/3,0)

Answer 6

divide by three
3x + y = 4
if y is zero, then x = 4/3
if x is zero, then y = 4
(4/3, 4)

Answer 7

y=1
x=1
9x1+3x1=12
hope you understand when you squish them together it means you multiply them it was simple.
and im in middle school.