ly_quest_2").innerHTML = "Sorry, it still has a solution in <i>x<sub>1</sub> =" + printable(xy[0]) + ", x<sub>2</sub> = " + printable(xy[1]) + "</i>. Please try again.";
    } else {
        document.getElementById("reply_quest_2").innerHTML = "Yes! When the lines are parallel, there is no solution.";
        document.getElementById("buttons_quest_2").style.display = 'none';
        quests[1] = 1;
    }
    draw_plot_named('system_1', 0, 0, false);
}

function done_system_1_quest_3() {
    xyxy1 = get_point