How do I fix the output of my fraction class's overloaded + operator?

I have a question about my fractionType class. I am coding it for an assignment and the assignment requires I overload the basic arithmetic operators (+, - , /, *) the logical operators (==, <, >, =<, =>) and the system operators (<<, >>) So far, the I have system operators working, as well as the multiplication and division operators. My problem came up when I tested the + and - operators. My input is hard coded as 2/4 and 1/8, but my output is 3/8. This is not right.

My code from fractionType.cpp

#include <iostream>
#include "fractionType.h"

fractionType::fractionType(){
}
fractionType::fractionType(int a, int b) {
  numerator = a;
  denominator = b;
}
fractionType fractionType::operator+(fractionType fraction) {
  fractionType anotherFraction;
  if (denominator = fraction.denominator) {

      anotherFraction.numerator = numerator + fraction.numerator;

      anotherFraction.denominator = denominator;
  }
if (denominator != fraction.denominator) {
    anotherFraction.numerator = ((numerator) * (fraction.denominator)) +         ((fraction.numerator) * (denominator));

    anotherFraction.denominator = denominator * fraction.denominator;
}
return anotherFraction;
}
fractionType fractionType::operator-(fractionType fraction) {

fractionType anotherFraction;

if (denominator = fraction.denominator) {

    anotherFraction.numerator = numerator - fraction.numerator;

    anotherFraction.denominator = denominator;
}
else {
    anotherFraction.numerator = (numerator * fraction.denominator) - (fraction.numerator * fraction.denominator);

    anotherFraction.denominator = denominator * fraction.denominator;
}

return anotherFraction;


}

My code from fractionType.h

#include <iostream>

class fractionType {
public: 
  fractionType(int a, int b);
  fractionType();
  fractionType operator*(fractionType fraction);
  fractionType operator/(fractionType fraction);
  fractionType operator+(fractionType fraction);
  fractionType operator-(fractionType fraction);
  friend std::ostream& operator<<(std::ostream& out, const fractionType &fraction) {
    out << fraction.numerator << '/' << fraction.denominator;
    return out;
}
friend std::istream& operator>> (std::istream& in, fractionType &fraction) {
    char c;
    in >> fraction.numerator >> c >> fraction.denominator;
    return in;
}
private:
int numerator, denominator;
};
#endif FRACTIONTYPE_H

and my source.cpp

#include <iostream>
#include "fractionType.h"

int main() {
  fractionType aFraction(2, 4);
  fractionType bFraction(1, 8);
  fractionType cFraction;
  cFraction = aFraction + bFraction;
  std::cout << cFraction << std::endl;
  system("PAUSE");
}

I cut out my operator* and operator/, because they work properly. I have no clue what I've done wrong, i've gone over the math over and over again before I posted this question. Is it because I didn't use a pointer? a const? Or is it something different? Thanks in advance for the help!