def exgcd(a,b,x,y):
    if not b:
        x,y = 1,0
        return a,x,y

    d,x,y = exgcd(b, a % b, y, x)
    temp = y
    y = x - a // b * y
    x = temp

    return d,x,y
if __name__ =='__main__':
    x,y = 0,0
    for i in range(int(input())):
        a,b,m = map(int,input().split())

        d,x,y = exgcd(a,m,x,y)
        if b % d : print('impossible')
        else:print( x *  b // d  % m )