Please help ease my mind!!!?

Question

I was helping my sister do math and maybe my brain's just gotten old but I couldn't sole this equation:

2x=y
x=2y-9

Solve for x and y


The problems are supposed to have real number solutions and for some reason no matter waht method I used, the answers I got wouldn't work when plugged in. Please help before I go insane!!!

Answer 1

you can substitude 2x for y and get:
x = 2(2x) -9
x = 4x - 9
-3x = -9
x = 3

plug that into the original
2(3) = y
6 = y
check, and it works
x = 3 and y = 6

Answer 2

1) 2x=y
2) x=2y-9

Plug equation 1 into equation 2 (substitute the y in equation 2 for the 2x in equation 1):
x=2(2x)-9
then multiply 2*2x, which equals 4x:
x=4x-9
subtract both sides by 4x:
-3x = -9
divide both sides by -3 to get the x by itself:
x = 3

then plug x = 3 into equation 1:
2x = y
2(3) = 6
so y = 6

then you can check your answers by plugging x = 3 and y = 6 into equation 2:
3 = 2(6)-9
3 = 12-9
3 = 3

hope that helped!

Answer 3

2x=y
x=2y-9 substitute 2x for y
x=2(2x)-9
x=4x-9 add 9 to each side
x+9=4x subtract x from each side
9=3x divide both sides by 3
x=3
substitute 2 for x in the ist equation
2*3=y
y=6

(3, 6)

Answer 4

2x=y;

=>x=y/2 (devide both side by 2)

for the next one,
x=2y-9;
=>2y-9=x;
=>2y=x-9;
=>2y=y/2-9; (put the value of x from the previous equation)
=>2y-y/2=9;
=>(4y-y)2=9;
=>3y=9*2;
=>y=18/3;
y=6;

First Equation, x=y/2;
=>x=6/2; ( from the 2nd equation where y=6)
x=3;

so , x=3, and y=6

Answer 5

Sub for y in the second eqn the first:
x = 2(2x) -9 = 4x - 9
3x = 9
x = 3
y = 2x = 2(3) = 6

Answer 6

Hahaha, you seem to be really stressed, I will try to help you out:

You have two equations, 2x=y and x=2y-9

As "y" equals to "2x", then we can rewrite the second equation as

x=2(2x)-9

Which in turn, we can rewrite as

x=4x-9

Now we have to add 9 to both sides (to maintain equality)

x+9=4x-9+9

Then we will have to substract x to both sides

x+9-x=4x-9+9-x

Then we have to reduce like-terms

9=3x

Now we divide both sides of the equation by 3.

9/3=3x/3

Then we get that

x=3

With this value, you can solve for "y" in the first equation by pluging 3 into the x.

2(3)=y

Getting finally

y=6

So you have that x and y are 3,6 respectively.

Quite easy huh? Hope that eases your mind!! =)

Answer 7

2x=y and x=2y-9

substitute what x equals into the equation to get 2(2y-9)=y. distribute that to get 4y-18=y. subtract the 4y to the other side to get -18=-3y. divide and y =6. plug that in to 2x=y to get 2x=6. divide that and get x=3.

answer is x=3, y=6

Answer 8

2x=y <-- Eq 1
x=2y-9 <-- Eq 2
Replace y in Eq 2 with 2x from Eq 1 getting:
x = 2(2x) -9
x = 4x -9
-3x = -9 x = 3
Put x = 3 in Eq 1 to get
2(3) = 6 = y

Answer 9

just plug in the y=2x to the equation x=2y-9
so,
x=2(2x)-9
x=4x-9
-3x=-9
x=3

Answer 10

plug the first one into the 2nd:

x = 2(2x) - 9
x = 4x - 9
-3x= -9
x = 3

plug this value back into the first equation:

y = 2x
y = 2(3)
y = 6