To solve for x, you undo what was done to x. The variable x is ...
- multiplied by y
- added to z
You "undo" these operations in the reverse order, so first we undo the addition of z. We accomplish that by adding the opposite of z:
... -10 -z = xy
Now, we undo the multiplication by y. We accomplish that by multipying by the reciprocal of y.
... (-10 -z)/y = x
We can rearrange this, if you like.
And, if you want, you can factor out the minus sign.
