When you run a function save the result into a variable, then pass that variable into the other functions as input parameters. More like this: const sum = calcSum(); const tax = calcTax(sum); Run the calcTax and calcSum functions only once.

The run fine, but I need to fix it like the comments above. Here is my code:

"use strict";

// Read the prices of the 3 elements from the DOM: back-price, calc-price, and text-price.

function showItems() {

const backPrice = document.getElementById("back-price");

const calcPrice = document.getElementById("calc-price");

const textPrice = document.getElementById("text-price");

// Read the text contents from the 3 DOM elements.

const backpackPrice = backPrice.textContent;

const calculatorPrice = calcPrice.textContent;

const textbookPrice = textPrice.textContent;

// Store the prices in an array

const pricesArray = [backpackPrice, calculatorPrice, textbookPrice];

return pricesArray;

}

// Calculate the total price of items

function calcSum() {

let subTotal = 0;

const prices = showItems();

subTotal = Number(prices[0]) + Number(prices[1]) + Number(prices[2]);

return subTotal;

}

// Declare the tax rate

function taxRate() {

const taxRate = 0.13; // The bookstore charges 13% sales tax.

return taxRate;

}

// Calculate the sales tax

function calcTax() {

let taxAmount = 0;

const sum = calcSum();

const rate = taxRate();

taxAmount = sum * rate;

return taxAmount;

}

// Calculate the final cost

function calcFinalCost() {

let finalCostAmount = 0;

const sum = calcSum();

const tax = calcTax();

finalCostAmount = sum + tax;

// Output the results

document.getElementById("sub-total").textContent = sum.toFixed(2);

document.getElementById("tax-amount").textContent = tax.toFixed(2);

document.getElementById("total").textContent = finalCostAmount.toFixed(2);

}

calcFinalCost();