trouble with parent / child

trouble with parent / child

I am attempting to make some changes on the screen when the user interacts with the quote price or the quantity of a line item.  I don't really understand what I'm doing with parent / child, but I did get a little bit of traction.  It's just not working.  

If someone can point me to a tutorial somewhere that would help me with parent / child examples that would be very helpful, or maybe you can answer my questions specifically.  

Here is some sample html: 
<table> 
<tr id="ABC123" sku="ABC123"><td class="itemno">ABC123 <input type="hidden" name="qdItem.SKU.N1" value = "ABC123"></td> 
                        <td class="liDescription">hello world</td> 
                <td><input type="text" name="qdItem.Price.N1" class="liQuotePrice" value = "27"> 
                        <input type="hidden" name="qdItem.orgPrice.N1" class="orgQuotePrice" value = "27"> 
                        <input type="hidden" name="qdItem.Cost.N1" class="qpc" value = "21.78"> 
                </td> 
                <td>35.11 <input type="hidden" name="qdItem.RPL.N1" VALUE = "35.11"></td> 
                <td>&nbsp;</td> 
                <td>22.86 <input type="hidden" name="qdItem.ICL.N1" VALUE = "22.86" ></td> 
                <td>&nbsp;</td> 
                <td><input type="text" name="qdItem.Quantity.N1" value="21" class="liQty"> 
                 
                         
                </td> 
                <td class="GM">19.3333333333%</td> 
                <td>&nbsp;</td> 
                <td>&nbsp;</td> 

                <td class="delcolumn"><img src="images/trash.png" class="icon" alt="delete" title="delete line item"></td> 
        </tr> 


        <tr id="DDD999" sku="DDD999"><td class="itemno">DDD999 <input type="hidden" name="qdItem.SKU.N2" value = "DDD999"></td> 
                        <td class="liDescription">a description of my item</td> 
                <td><input type="text" name="qdItem.Price.N2" class="liQuotePrice" value = "43"> 
                        <input type="hidden" name="qdItem.orgPrice.N2" class="orgQuotePrice" value = "43"> 
                        <input type="hidden" name="qdItem.Cost.N2" class="qpc" value = "21.9996152147"> 
                </td> 
                <td>35.46 <input type="hidden" name="qdItem.RPL.N2" VALUE = "35.46"></td> 
                <td>&nbsp;</td> 
                <td>22.88 <input type="hidden" name="qdItem.ICL.N2" VALUE = "22.88" ></td> 
                <td>&nbsp;</td> 
                <td><input type="text" name="qdItem.Quantity.N2" value="22" class="liQty"> 
                 
                         
                </td> 
                <td class="GM">48.8381041518%</td> 
                <td>&nbsp;</td> 
                <td>&nbsp;</td> 

                <td class="delcolumn"><img src="images/trash.png" class="icon" alt="delete" title="delete line item"></td> 
        </tr> 

</table> 

Here is some javascript that is not working:   

$(document).ready(function(){ 
    

    $(this).find('.liQuotePrice').change(function() { 
    var content = $('.orgQuotePrice').val(); 
        console.log(content + '(original price'); 
         
            if ($('.liQuotePrice').val() != content) { 
                //if ($('.liQuotePrice').val() != content  || ($('.liQuotePrice').val() == '')) { 
            content = $('.orgQuotePrice').val(); 
            console.log('quote price was changed') 

  
//alert($(this).parent('td').parent('tr').attr('sku')); 
var SKU =  $(this).parent('td').parent('tr').attr('sku'); 


if ($(SKU).children('td').eq(8)) { 
//console.log(SKU); 

var cost = $(".qpc").val(); 
var nqp = $(".liQuotePrice").val(); 
var newGM = ( ((nqp - cost)/nqp) * 100) ; 

newGM  = newGM.toFixed(2) + "%"; 

 $(SKU).children('td').eq(8).html(newGM); 

 console.log(newGM + ' ' + SKU); 
  
 cbutton(); 
} 
  
 } 


}); 
}); 

****************** 

How do I write my new calculation in the 9th table data element of the row in which I'm editing?  There could be lots of rows (more than one anyway).  I will also need to write new calculations to other table data elements in the same row.   

Linda