Solution for a set of non-linear equations
No problem. If a solution exists, you find it manually assuming you have precise enough calculator.

The 3rd equation has D in a place which is redundant. The only effective variable is K. Multiply with the denominator and you have a simple linear equation for K. Solve K.

Insert K to the 1st and 2nd equation. Both can be reduced to same form A^D=B where A and B are numerical values. You find D as logarithm D=ln(B)/ln(A)

If both equations give the same D you have a solution.

BTW the problem is not well defined. If there's more equations than there are variables, you should define 


how much you allow the left sides be different than zero and 
what is the criteria for the best solution, if there were a set of possible (K,D) pairs which satisfy the max differece to zero declaration.