Can you help me?

Question

I need help solving this equation:

y = 5 - x
3x - 4y = -20

and this equation

x - 2y = 5
12x + 4y = -10

Thanks!!!!!!

Answer 1

y = 5 - x
3x - 4y = -20

x=0,y=5

x - 2y = 5
12x + 4y = -10

x=0,y=-2.5.

Answer 2

Substitute Method

y = 5 - x - - - - - - - -Equation 1
3x - 4y = - 20- - - - -Equation 2
- - - - - - - - - -

Insert the y value equation 1 into equation 2

3x - 4y = - 20

3x - 4(5 - x) = - 20

3x - 20 + x = - 20

4x - 20 = - 20

4x - 20 + 20 = - 20 + 20

4x = 0

4x/4 = 0/4

x = 0

The answer is x = 0

Insert the x value into equation 1

- - - - - - - - - - - - - - - -- - - - --

y = 5 - x

y = 5 - 0

y = 5

The answer is y = 5

Insert the y value into equation 1

- - - - - - - - - - - - - - - - - - - - - -

Check for equation 1

y = 5 - x

5 = 5 - 0

5 = 5

- - - - - - - - -

Check for equation 2

3x - 4y = - 20

3(0) - 4(5) = - 20

0 - 20 = - 20

- 20 = - 20

- - - - - - - - - -

The solution set is { 0, 5 }

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Problem 2

Elimination by addition method

x - 2y = 5- - - - - - - -Equation 1
12x + 4y = - 10- - - -Equation 2
- - - - - - - - - - -

multiply eqation 1 by 2

x - 2y = 5

2(x) - 2(2Y) = 2(5)

2x - 4y = 10

- - - - - - - - - - -

2x - 4y = 10
12x + 4y = - 10
- - - - - - - - --

14x = 0

14x/14 = 0 / 14

x = 0

The answer is x = 0

Insert the x value into equation 1

- - - - - - - - - - - - - - - - - - - - -

x - 2y = 5

0 - 2y = 5

- 2y/2 = 5/- 2

y = - 2.5

The answer is y = - 2.5

Insert the y value into equation 1

- - - - - - - - - - - - - - - - - - - - - -

Check for eqation 1

x - 2y = 5

0 - 2(- 2.5) = 5

5 = 5

- - - - - - - - - - - - -

Check for equation 2

12x + 4y = - 10

12(0) + 4(- 2.4) = - 10

0 + (- 10) = - 10

- 10 = - 10

- - - - - - - - - - - - - -

The above systems of equtaion was done by the elimihation by addition method. The substitute method also works.

- - - - - - - - -

The solution set is { 0, - 2.5 }

- - - - - -s-

Answer 3

y = 5 - x
3x - 4y = -20


you put (5-x) instead of y in the second eq.

3x - 4(5-x) = -20
3x -20 +4x = -20
3x+4x = 0
7x = 0
x = 0
then put it in the first equation where y = 5-x
then y = 5
--------------------------------------
x - 2y = 5
12x + 4y = -10


x = 5 + 2y

then 12 (5+2y) + 4y = -10
60 + 24y + 4y = -10
28y = -70
y = - 2.5

then plug it in the first equation
x = 5 +2y
x = 5 + 2(-2.5)
= 5-5 = 0

Answer 4

y = 5 - x
3x - 4y = -20
sub y in equation 2
3x-4(5-x)=-20
3x-20+4x=-20
7x-20=-20
adding 20
7x=0
x=0
sub in equation 1
y=5-0=5

2.x - 2y = 5
12x + 4y = -10
eqn.!*2
2x-4y=10
12x+4y=-10
adding
14x=0
x=0
sub in eqn.1
0-2y=5
y=-5/2

Answer 5

First one ..........
y = 5 - x i.e. x + y = 5
3x - 4y = -20
Multiply the first eqn with 4 and add the resultant eqn to the second eqn .... this gives you ...... 7x = 0 and so, x = 0
That gives y = 5

Second one .........
x - 2y = 5
12x + 4y = -10 i.e. 6x + 2y = -5
Add these two eqns ..... gives you .......... 7x = 0 and so x = 0.
Then y = -5/2

Answer 6

5 - x = y
Multiply this equation by 3
15 - 3x = 3y

Add on to the other equation

-y = -5
y = 5

Plug into equation to solve for x

5 - 5 = y

x = 0

x = 0, y =5

Second one..

2x - 4y = 10

Add on to other equation

16x = 0
x = 0

Plug into equation to solve for y

0 - 2y = 5

y = -2.5

x = 0, y = -2.5

Answer 7

3x-4y=-20
3x-4(5-x)=-20
3x-20+4x=-20
7x-20=-20
7x=-20+20
7x=0
x=0
y=5-x
y=5-0
y=5
(1)3x-4y=-20
3(0)-4(5)=-20
0-20=-20
-20=-20
next
x-2y=5
x=5+2y

12x+4y=-10
12(5+2y)+4y=-10
60+24y+4y=-10
28y=-10-60
28y=-70
y=-70/28
y=-2.5
x-2y=5
x-2(-2.5)=5
x+5=5
x=5-5
x=0

12x+4y=-10
12(0)+4(-2.5)=-10
0-10=-10
-10=-10

Answer 8

I agree with them.

Answer 9

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