The answer is x = -2.
Here are the steps.
1. Add 2x to both sides ( -13 = 8x + 7 + 2x ).
2. Simplify 8x + 7 + 2x to 10x + 7 ( -13 = 10x + 7 ).
3. Subtract 7 from both sides ( -13 - 7 = 10x ).
4. Simplify -13 - 7 to -20 ( -20 = 10x ).
5. Divide both sides by 10 ( -20/10 = x ).
6. Simplify 20/10 to 2 ( -2 = x ).
7. Lastly just switch sides and u get x = -2.