-10 = -1 -x
First, you can add x to both sides
-10 ( + x ) = -1 - x ( + x ) *The -x and +x would cancel each other out.
= -10 + x = -1
Then, you can add 10 on both sides.
= -10 (+10) +x = -1 (+10) *The -10 and +10 would cancel each other out.
Your final answer should be x = 9. I hope this was helpful :)