Generally, something like $('#q25 input') is the way to target most fields when they're not in a table. I like to make it easier and assign a CSS class to the fields I'm working with and just use that instead of the ID, but doing it this way is also fine.

Targeting the fields in a table is a little trickier, just because these fields can be repeatable. If you look at the HTML for a repeatable field in a table, you'll see something like this:

<input id="Field3(1)" class="singleline cf-xlarge form-ui-valid user-success" type="text" vo="e" list="datalist3" maxlength="4000" name="Field3(1)"></input>

Basically, the ID is the same as the column's ID with a number appended to the end. This is to ensure the uniqueness of each ID attribute. This is also why something like $('#q3 input') will not target this field.

I've found it is easiest to target each row or column and then find the correct fields within that context. The most straightforward way to reference these fields is to give the column a CSS class, and then look for fields with that class in each row.

Here's an example that calculates the subtotal for table rows:

$(document).ready(function () {
    $('.cf-table-block').on('blur', 'input', sumtotal);
    function sumtotal() {
        var sum = 0;
        $('.cf-table-block tbody tr').each(function () {
            var s = 0;
            $(this).find('.price input').each(function () {
                s += parseNumber($(this).val());
            })
            $(this).find('.subtotal input').val(s);
            sum += s;
        });
        $('.total input').val(sum);
    }
    function parseNumber(n) {
        var f = parseFloat(n); //Convert to float number.
        return isNaN(f) ? 0 : f; //treat invalid input as 0;
    }
});

Basically, this code waits for the user to leave a field in the table, and then, for each table row, finds each field with the price CSS class, adds them together, and puts the total in the appropriate field.

Even though you're doing something different, this sort of structure should probably work for you. Watch for a blur event on .cf-table-block, then go through each row and perform the calculations you want.