how to solve two equations in one variable

How can i calculate the value of the variable (X) from these two equations, if i know the value of J and D

Answer 1

[David Hill]

syms x;
J=
D=
eq=exp(-x)-52*x^3==J/D;%combine the equations yourself
vpasolve(eq,x);

[David Hill]

You did not use the correct equation.

eq=exp(-x)-52*x^3==J/D;