er = Number(document.getElementById('linear_multiplier').value);
    var row = document.getElementById('linear_row2');
    if(multiplier != 0) {
        row.innerHTML = printable_eq(multiplier, "x<sub>1</sub>", 2 * multiplier, "x<sub>2</sub>", 3 * multiplier);
    } else {
        row.innerHTML = "Except for 0, yes.";
        hidden_quests[0] = 1;
    }
}

//////
/// underspecified
function change_s3_1_1() {}
function change_s3_1_2() {}
function change_s3_1_3() {}
function change_s3_1_4() {}
function change