Question

How do you solve `x=-4y` and `3x+2y=20`?

Answer 1

See the entire solution process below:

Explanation:

Step 1) Because the first equation is already solved in terms of `x`, substitute `-4y` for `x` in the second equation and solve for `y`:

`3x + 2y = 20` becomes:

`3(-4y) + 2y = 20`

`-12y + 2y = 20`

`-10y = 20`

`(-10y)/color(red)(-10) = 20/color(red)(-10)`

`(color(red)(cancel(color(black)(-10)))y)/cancel(color(red)(-10)) = -2`

`y = -2`

Step 2) Substitute `-2` for `y` in the first equation and calculate `x`:

`x = -4y` becomes:

`x = -4 * -2`

`x = 8`

The solution is: `x = 8` and `y = -2` or `(8, -2)`