Question

Solve the system of equations using substitution and Elimination

-x - 9y= 16

10x+ 20y=20

Answer 1

Greetings!

Answer:

y =
`(-18)/(7)` and x =
`(50)/(7)`

Explanation:

To solve simultaneous equations, you need to have the number in front of both x's or y's the same. (signs doesn't matter)

To get -x to -10x we simply need to multiply the first equation by 10:

-x * 10 = -10x

-9y * 10 = -90y

16 * 10 = 160

-10x - 90y = 160

Now we can add the two equations:

-10x + 10x = 0

-90y + 20y = -70y

160 + 20 = 180

-70y = 180

70y = -180

7y = -18

y =
`(-18)/(7)`

Now plug
`(-18)/(7)` into the second equation:

10x + 20(
`(-18)/(7)`) = 20

10x -
`(360)/(7)` = 20

Move the
`(360)/(7)` over to the other side, making it a positive:

10x = 20 +
`(360)/(7)`

10x =
`(500)/(7)`

Divide both sides by 10:

x =
`(50)/(7)`

So y =
`(-18)/(7)` and x =
`(50)/(7)`

Hope this helps!