Solve the system by substitution. 3x - y = -7, x + y = -9?

Answer 1

That's a statement with a question mark at the end. What is YOUR question?

Why not first solve for X in the x+y = 9 equation? Then use that for the X in the first equation.

Answer 2

x + y = -9
3x - y = -7

To solve a system of equations using substitution, take one of the equations and solve for a variable:
x + y = -9
subtract y from both sides:
x = -9 - y

now take this value and plug it in for x in the other equation:
3x - y = -7
3(-9 - y) - y = -7

now solve for y:
-27 -3y - y = -7

combine like terms and add 27 to both sides:
-4y = 20

divide both sides by -4
y = -5

now plug this into one of the equation to find the value of x:
x + y = -9
x - 5 = -9
x = -4

CHECK: plug both values into the equations to make sure they are correct:
-4 -5 = -9
-9 = -9

3(-4) -(-5) = -7
-12 + 5 = -7
-7 = -7

x = -4, y = -5

Answer 3

solve x + y = -9 for x. x = -9 - y

insert x = -9 - y for x in 3x - y = -7

3(-9 - y) - y = -7 distribute the 3 over the parentheses

-27 - 3y - y = -7 simplify and solve for y

-27 - 4y = -7

-4y = -7 + 27

-4y = 20

y = 20/-4

y = -5

Now put the y = -5 value into one of the equations and solve for x.

x + (-5) = -9

x - 5 = -9

x = -9 + 5

x = -4

Your answer is (-4, -5)

Answer 4

3x - y = -7
x + y= -9

add the Ys the then combine

4x= -16

divide by -4

x= -4... then substitute
-4 + y= -9
+ 4 from the sides

x= 4
y= -5

Answer 5

first find ONE variable
x + y = -9
x = -9 - y

3(-9 - y) - y = -7
-27-3y-y = -7
-4y = -7 + 27
-4y = 20
y = -5

OR

x + y = -9
y = -9 - x

3x - (-9 - x)= -7
4x -9 = -7
4x= -7 + 9
4x = 2
x = 2/4

Answer 6

3x - y = -7 ...........(1)

x + y = -9.............(2)

Taking (2)

y = -9 - x..............(3)

Substitute (3) into (1)
-->

3x - (-9 - x) = -7

3x + 9 + x = -7

4x = -16

x = -4.................(4)

Substitute (4) into (2)

-4 + y = -9

y = -5

x = -4
y = -5

Answer 7

algebra already gives me a concussion thank u very much