C++ equation solver read/write text in class

Hello here's the codes structure, I have a class textRead,this class reads a text from text file which is a equation ex: "3*x*x+2*x-13", gets the number from the user like x = 3 go write 3 instead of x and calculate the result and write another text file. My class:

class textRead

{

private:

string equation, result;

int number;

fstream fileptr;

public:

textRead(); // default constructor

openfile(); // open text file

userinput(); // get x value from the user

Display(); // calculate and write another text file

}