solve this math problem?

Question

7x-77= -7y
5x-5y= -15

its one problem. use the substitution method. show work if you can. im lost

Answer 1

Start with the top equation to use for substitution.

7x - 77 = -7y
-x + 11 = y

Substitute that into the second equation

5x - 5(-x + 11) = -15
5x + 5x - 55 = -15
10x = 40
x = 4

Then, use that solution in the first to solve for y.

7(4) - 77 = -7y
28 - 77 = -7y
-49 = -7y
7 = y

So, the solution is x = 4 and y = 7.

Answer 2

Look at the second eqn; note that it is in the form ax + by = c where a,b,c are constants. Put each eqn in that form, figure out a way to eliminate one of the variables, find the value of the other and you are home. First, get the first eqn in the proper form:
7x + 7y = 77 Now get the second eqn up:
5x - 5y = 15 Get these all factored out:

x + y = 11 by dividing out by 7
x - y = 3 by dividing out by 5
Normally it is not so easy and you have to find a common term; but I digress. Just add the two eqns:
2x = 11 + 3 = 14 so x = 14/2 = 7 and sub it back into the first eqn:
7 + y = 11 or y = 11- 7 = 4

Answer 3

What you have to do is solve one of the equations for either x or y

5x-5y=-15
5x=5y-15 (divide both sides by 5)
x=y-3
y=x+3

plug that into the other equation

7x-77=-7(x+3)
7x-77=-7x-21
14x=56

x=4
then plug that into other equation to find y

5(4)-5y=-15

20-5y=-15
-5y=-35

y=7

so x=4, y=7

Answer 4

Divide 7x-77= -7y by 7,
x-11 = -y

Divide 5x-5y= -15 by 5
x-y = -3

Substitute -y = x-11 into the second equation,
x+(x-11) = -3

Solve for x and y,
x = 4
y = 7

Answer 5

7x-77= -7y ....(1)

So x - 11 = -y ... (1a)
ie x = 11 - y .... (1b)

5x-5y= -15 ... (2)
So x - y = -3 ...(2a)

Substiute equation (1b) into equation (2a)

x - y = -3

so (11 - y) - y = -3

So 11 - 2y = -3

So 2y = 14 (As 11 - 14 = -3)

thus y = 7

From equation (2)

5x-5y= -15

5x - 35 = -15
5x = 20
x = 4

Check in Equation (1)

7x - 77
= 28 - 77
= -49
= -7 x 7
= -7y QED!!!

So the solution is x = 4, y = 7

Answer 6

-7y = 7x - 77
y = -x + 11

5x - 5( -x +11 ) = -15
5x + 5x - 55 = -15
10x - 55 = -15
10x = 40
x = 4

5( 4 ) - 5y = -15
20 - 5y = -15
-5y = -35
y = 7

answer: x= 4 and y= 7 or (4, 7)

Answer 7

Divide first equation by 7, divide second equation by 5. Solve for Y in the first equation. Plug into the second and you should get:
x=4, y=7

Answer 8

so we need to find what one x or y =

5x-5y = -15.... add 5y to both sides
5x=5y-15....divide by 5
x=y-3

aha - now we can substitue

7x-77 = -7y
7(y-3) - 77 = -7y

7y - 21 -77 = -7y
7y - 98 = -7y....add 7y to both sides
14y - 98 = 0......add 98 to both sides
14y = 98 divide by 14
y = 7

5x - 5(7) = -15
5x - 35 = -15....add 35 to both sides
5x = 20

u got it from here

Answer 9

2x + 2y = 20 utilising the simultaneous approach 2x - 2y = 4 ____________ 4x = 24 ( divide by 4) x = 6 substitute x in one in each and every of the two equations 2x + 2y = 20 2 (6) + 2y = 20 12 +2y = 20 2y = 20 - 12 2y = 8 (divide by 2) y = 4 answer : X = 6 , Y = 4

Answer 10

Start by simplifying and rearranging to get:
x + y = 11
x - y = -3
It is obvious that 2y = 14, y = 7, and x = 4.