max=20; 

answer = Math.floor(Math.random()*max)+1; 

left = Math.floor(Math.random()*answer); 

right = answer - left; 

equation = left+" + "+right+" = "; 

key = (answer*2)+1; answerkey = "<input type=hidden name=EQUATION value="+key+" >"; 

document.write(equation); 

document.write(answerkey);