[latex] -7-x=3\\ -x=10\\ x=-10[/latex]

[latex]-7 - x = 3[/latex] [latex]- x = 3 + 7[/latex] [latex]- x = 10[/latex] [latex]x = \frac{10}{-1} [/latex] [latex]\boxed{x=-10}[/latex]