Thank you for the reply.  maskWhiteboard is which  other movie clip?  I'm a little confused

Thank you again.  However, when I do this, it won't draw anywhere.  I put a new movie clip on the stage with an instance name of whiteboardMask.  Then, I put the code, changing it to whiteboardMask instead of maskWhiteboard.  Now, when I test it, it will not draw anywhere.

import flash.display.MovieClip;

import flash.events.MouseEvent;

var lines:MovieClip;

var isMoving:Boolean = false;

var linesColor:Number = 0x000000;

var linesSize:uint = 1;

var equations:Array = new Array;

var equationsAnswers:Array = new Array;

var score:uint = 0;

var questionsAsked:uint = 0;

var answer:String = new String;

var drawable:MovieClip = new MovieClip;

equations = ["x + 7 = 13", "x - 8 = 23"];

equationsAnswers = ["6", "31"];

lines = new MovieClip();

stage.addEventListener(MouseEvent.MOUSE_DOWN, startLines);

stage.addEventListener(MouseEvent.MOUSE_MOVE, drawLines);

stage.addEventListener(MouseEvent.MOUSE_UP, stopLines);

checkbtn.addEventListener(MouseEvent.CLICK, newquestion);

stage.addChild(lines);

drawable.addChild(lines);

drawable.mask=whiteboardMask;

function startLines(e:MouseEvent) : void {

    isMoving = true;

    lines.graphics.lineStyle(linesSize, linesColor, 1.0);

    lines.graphics.moveTo(mouseX, mouseY);

}

function drawLines(e:MouseEvent):void {

    if (isMoving){

        lines.graphics.lineTo(mouseX, mouseY);

    }

}

function stopLines(e:MouseEvent):void {

    isMoving = false;

}

function newquestion(e:MouseEvent):void {

    answer = inputAnswer.text;

    if (answer == equationsAnswers[questionsAsked]){

        score ++;

    }

    questionsAsked++;

    scoreshow.text = score + ":" + questionsAsked;

    question.text = equations[questionsAsked];

    inputAnswer.text = "";

}

question.text = equations[questionsAsked];

Any help would be appreciated.

thank you, I'm an idiot.

It works perfectly now.

Thank you again.  Is there an easy way to erase the entire whiteboard?  to get rid of all the "lines" on the whiteboard?

Thank you. WOW again I completely miss the obvious.