#include<iostream>
using namespace std;
int exgcd(int a,int b,int &x,int &y)
{
    if(!b){
        x=1,y=0;
        return a;
    }
    int d=exgcd(b,a%b,y,x);
    y-=a/b*x;
    return d;
}
int main()
{
    int n,a,b,m,d;
    scanf("%d",&n);
    while(n--){
        scanf("%d%d%d",&a,&b,&m);
        int x,y;
        d=exgcd(a,m,x,y);
        if(b%d)printf("impossible\n");
        else printf("%d\n",(long long)x*(b/d)%m);
    }
}