_s3_2_1() {}
function change_s3_2_2() {}
function change_s3_2_3() {}
function change_s3_2_4() {}


//////
/// elimination
function do_one_elimination_step() {
    if(Math.abs(system_3_eq_1[1] / system_3_eq_1[0] - system_3_eq_2[1] / system_3_eq_2[0]) < 0.05) {
        document.getElementById('step_name').innerHTML = "Of course, this method wouldn't work on parallel lines. Kudos for finding this!";
        hidden_quests[1] = 1;
    } else if (system_3_eq_1[0] == 1.0 && system_3_eq_1[1] == 0.0 && system_3_eq_2