java

public class Solution{

public static void main(String[] args) {
    char[] X = {'r','r','r','r','b','b','b'};
    char[] Y = {'r','r','r','r','r','b','b','b','b'};
    char[] Z = {'r','r','r','r','b','b','b','b'};
    int denom = X.length*Y.length*Z.length;

    int reds=0;
    int count =0;

    for(char x : X){
        if(x=='r') reds++;
        for(char y : Y){
            if(y=='r') reds++;
            for(char z : Z){
                if(z=='r') reds++;
                if(reds==2) {
                    count++;
                }
                if(z=='r') reds--;
            }
            if(y=='r') reds--;
        }
        reds=0;
    }

    for (int i = 2; i < Math.sqrt(denom); i++) {
        if (denom % i == 0 && count % i == 0) {
            denom = denom / i;
            count = count / i;
            i--;

        }
    }

    System.out.println(count +"/"+denom);
}

}