X+2y=-1 and 4x-4y=20 solve by substitution

To do this problem you would first need to factor out a variable, which in this case I would want to do the first equation because it is isolated. Now the equations would look like this:

x = -2y - 1

4x - 4y = 20

Since we know that x is now equal to -2y - 1 we can plug it in to the x value in the second equation:

4 (-2y -1) - 4y = 20

-8y -4 - 4y

-12y - 4 = 20

-12y = 24

y = -2

Now that we know the y value plug the y value to one equation to find the x, I will be using the first equation

x + 2(-2) = -1

x - 4 = -1

x = 3

Solutions:

y = -2

x = 3

answer: 140

step-by-step explanation:

so just add all then it will be your answer but i am not pretty sur eif it is but hope this i am here to people

step-by-step explanation:

12: 00 p.m. to 7: 00 p.m. is a total of 7 hours.

4: 00 p.m. to 7: 00 p.m. is a total of 3 hours.

this means that from 4: 00 p.m to 7: 00 p.m. this represents 3/7 of what was lost from 12: 00 p.m. to 7: 00 p.m.

after knowing this, after doing 11,600 - 6,800 = 4,800

4,800 represents 3/7 of what was lost for 7 hours.

we then divide 4,800 by 3 which gets 1,600.

because we know that 1,600 represents 1/7 of how much water was lost, we just have to multiply by 7, which gets 11,200.   after adding 11,200 to how much water was left at 7: 00 p.m. which was 6,800. 11,200 + 6,800 = 18,000

this means that the pool originally had 18,000 gallons in the pool.

you can also check your work by doing 18,000 - 4(1600), which becomes           1800 - 6400 which gets you 11,600.