What if 3-x=-4, then what is x equal to?

Here we see that.

3-x=-4,so value of x=to We have to arrange it variable one side and another side constant

1. First put - x in right hand side it's sign will change it becomes x. Now put-4 to left hand side it becomes 4
2. Now solve it. Like that
3. 3+4=x
4. 7=x. Value of x is 7.

I thinks you understood it