Question

How do you solve `-8x = - 21- 9x`?

Answer 1

`x=-21`

Explanation:

`"collect terms in x on the left side of the equation"`
`"and numeric values on the right side"`

`"add 9x to both sides"`

`-8x+9x=-21cancel(-9x)cancel(+9x)`

`rArrx=-21`

`color(blue)"As a check"`

Substitute this value into the equation and if both sides are equal then it is the solution.

`"left "=-8xx-21=168`

`"right "=-21+(-9xx-21)=-21+189=168`

`rArrx=-21" is the solution"`

Answer 2

`x=-21`

Explanation:

`-8x=-21-9x`

We need to put every expression with `x` on the left side of the equals sign and the number on the right.

`-8x+9x=-21`

`x=-21`