Answer 1

try this
https://code.sololearn.com/W1XI2hcEWMuu/?ref=app

Answer 2

Captain HRK

function main(){

var x = document.getElementById("a");
var y=document.getElementsByTagName("hr");
y[0].style.width=x.value+"px";

}

OR
function main(){
var y=document.getElementsByTagName("hr");
y[0].width=document.getElementById("a").value;
}