First, subtract 2d from both sides. Your problem should look like: 3d + 8 - 2d = -7. Second, simplify 3d + 8 - 2d to get d + 8. Your problem should look like: d + 8 = -7. Third, subtract 8 from both sides. Your problem should look like: d = -7 - 8. Fourth, simplify -7 - 8 to get -15. Your problem should look like: d = -15, which is your answer.
Hopefully this helps, I'm not exactly sure what you meant by "is equations," but this is how you solve the problem.
