@Justeena I took you code and added the Sum part
 

Qualtrics.SurveyEngine.addOnload(function() {
    // Access to the question div
    let ques = document.getElementById('Questions');

    // Access to the text boxes within the side-by-side question
    let text = jQuery("#" + this.questionId + " input[type='text']");

    // Access to the checkboxes within the side-by-side question
    let checkboxes = jQuery("#" + this.questionId + " input[type='checkbox']");


    let sumDisplay = document.createElement("div");
    sumDisplay.id = "sumDisplay";
    sumDisplay.style.fontWeight = "bold";
    sumDisplay.innerText = "Sum: 0";
    ques.appendChild(sumDisplay);

    function updateSum() {
        let sum = 0;
        text.each(function() {
            if (!this.disabled && this.value !== "") {
                sum += parseInt(this.value, 10);
            }
        });
        sumDisplay.innerText = "Sum: " + sum;
    }

    // Validates if selected is clicked and then disables the matching text box
    ques.addEventListener("click", function() {
        for (let j = 0; j < checkboxes.length; j++) {
            if (checkboxes[j].checked) {
                text[j].disabled = true;
                text[j].value = ""; // Clear the text box if the checkbox is checked
            } else {
                text[j].disabled = false; // Enable the text box if the checkbox is unchecked
            }
        }
        updateSum();
    });

    // Allow only numbers in the text boxes
    text.on('input', function() {
        this.value = this.value.replace(/[^0-9]/g, '');
        updateSum();
    });
});

Qualtrics.SurveyEngine.addOnReady(function() {
    // Access to the question div
    let ques = document.getElementById('Questions');

    // Access to the text boxes within the side-by-side question
    let text = jQuery("#" + this.questionId + " input[type='text']");

    // Access to the checkboxes within the side-by-side question
    let checkboxes = jQuery("#" + this.questionId + " input[type='checkbox']");

    function updateSum() {
        let sum = 0;
        text.each(function() {
            if (!this.disabled && this.value !== "") {
                sum += parseInt(this.value, 10);
            }
        });
        document.getElementById("sumDisplay").innerText = "Sum: " + sum;
    }

    // Validates if selected is clicked and then disables the matching text box
    ques.addEventListener("click", function() {
        for (let j = 0; j < checkboxes.length; j++) {
            if (checkboxes[j].checked) {
                text[j].disabled = true;
                text[j].value = ""; // Clear the text box if the checkbox is checked
            } else {
                text[j].disabled = false; // Enable the text box if the checkbox is unchecked
            }
        }
        updateSum();
    });

    // Allow only numbers in the text boxes
    text.on('input', function() {
        this.value = this.value.replace(/[^0-9]/g, '');
        updateSum();
    });
});

Qualtrics.SurveyEngine.addOnUnload(function() {
    // Access to the text boxes within the side-by-side question
    let text = jQuery("#" + this.questionId + " input[type='text']");

    // Access to the checkboxes within the side-by-side question
    let checkboxes = jQuery("#" + this.questionId + " input[type='checkbox']");

});