X = -10
Because it is the "absolute value" of "10"
Here's why
-X - 10 = 0, right ?
So, now we have to add a positive 10 to each of our sides to get one step closer to our answer
-X + 10 = 0 ⬅️cancel this
0 + 10 = 10 ⬅️keep this
We can multiply by a negative 1 (-1 )
10(-1) = -10
0(-1) = -0
So that's how we found out that X = -10