if(almost(a11 / a21, a12 / a22) && almost(a11 / a21, a13 / a23))
    {
        if(almost(a11 / a21, b1 / b2))
        {
            document.getElementById("reply_quest_5").innerHTML = "Well, they are linearly dependent, this means they are the same plane. Still, any point on this plane is a solution.";
        } else {
            document.getElementById("reply_quest_5").innerHTML = "Exactly! Parallel planes in a system have their matrix part linear dependent and the vector part — not.";
            