Can anyone please explain how to solve for y and x through substitution and elimination? If possible, step by step please.

You can use this as your example:
2y - 3x = 30
4y + 3x = 24

Question

Can anyone please explain how to solve for y and x through substitution and elimination? If possible, step by step please.

You can use this as your example:
2y - 3x = 30
4y + 3x = 24

anonymous · Answer

Add the equations 

6y = 54
y = 9

mimi_x3 · Answer

elimination:
2y - 3x = 30 
                     -
4y+ 3x = 24

-2y = 6
y = -3 
To find x sub it into 2y - 3x = 30

anonymous · Answer

:< I'm afraid I don't quite understand, Ishaan.

mimi_x3 · Answer

lols , btw , yu cant add the 2 equations in elimination xDD

anonymous · Answer

2y - 3x = 30
4y + 3x = 24
Now add these equations 

2y + 4y +3x -3x = 30 + 24
6y = 54
y =  9

anonymous · Answer

Thanks, Mimi. (: I understood it! ^(OwO)^ 

But how about through substitution? o3o

anonymous · Answer

Mimi http://www.wolframalpha.com/input/?i=2y+-+3x+%3D+30%2C+4y+%2B+3x+%3D+24

mimi_x3 · Answer

ohh yeah my bad

mimi_x3 · Answer

i read the equation wrongly xDD

anonymous · Answer

2y -3x = 30
2y - 30 =3x
This is the fist equation now second 
4y + 3x =24
Now substitute the value of 3x
4y + 2y -30 = 24
6y =54
y=9

mimi_x3 · Answer

2y - 3x = 30
                    +
4y + 3x = 24
6y = 54
y = 9

anonymous · Answer

Now substitute y in first 
2x9 -3x = 30
18-30 = 3x
6-10=x
x=-4

mimi_x3 · Answer

lols , my way is the elimination method btw

anonymous · Answer

how do u know when to use substitution and when to use elimination

anonymous · Answer

spicenangel depends on the equation. if i see same co-efficient then I eliminate or if see some multiplication that makes co-efficient same. elimination is faster method you will get to know after enough practice.

anonymous · Answer

So, it's like this, through elimination, based on the site you gave me, and info you guys gave me, and from what I know?

                       eliminate x
   2y - 3x = 30
+4y + 3x = 24
   6y + 0x = 54

6y + 0x = 54
6y = 54

Then, you divide those two by 6, to erase the 6 from the y.

y = 9

                        eliminate y
2y - 3x = 30

Replace y with your y with the y at the first equation.

2(9) - 3x = 30

18 - 3x = 30

Then you transpose 18 to the other side because you need to have one side with all the numbers with variables, and the other side with numbers only. ((18 becomes -18 because it was transferred to the other side, right?))

-3x = 30 - 18

And... this was where I was stumped. Do you divide the two with -3 already or do you subtract 30 and 18 first?

mimi_x3 · Answer

-3 x = 12
-x = 4
x= -4

anonymous · Answer

Ah, so I subtract the two first. Thanks. owo