Question

2n^3-3m=5 solve for n

Answer 1

Not solvable over the set of Real numbers. Use a program like Mathematica if you want a numeric answer.

Answer 2

If it can be in terms of m, you can say that \[n = \pm \sqrt{(5-3m) / 2}\] Otherwise you only have one linearly dependent equation, when you would need 2.