using loop to calculate the interest with unknown time [closed]

I have to to write a program that could help me to calculate the interest rate with unknown time

the credit is about 10000 and the is 7% and to pay in instalments 1500 i want the redemption and the remain, when the program reach 0 remain should stop

double kredit = 10000;

const double ZinsenProzent = 0.07;

double Teilgung, Zinsen, Restschuld = 10000, Annuitaet = 1500;

do {
    Zinsen = Restschuld * ZinsenProzent;
    cout << "zinsen" << Zinsen << endl;

    Teilgung = Annuitaet - Zinsen;
    cout << "teilgung" << Teilgung << endl;

    Restschuld = Restschuld - Teilgung;
    cout << "rest ist" << Restschuld << endl;
} while (Restschuld > 0);

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