Hello there! I can help you! So we know that the Sahara Desert is 3.5 million square mile in area, and there are 2.79 * 10^7 square feet in a square mile. Square feet is a smaller unit than square mile. To find the amount of square feet, we can do this by multiplication. 3.5 million in scientific notation is 3.5 * 10^6. Let's multiply the constants first. 3.5 * 2.79 is 9.765. We don't need to simplify that, because it's less than 10. We are multiplying the based by the same power, so we can add the exponents. 6 + 7 is 13. That makes the expression in scientific notation 9.765 * 10^13 or 97,650,000,000,000 in standard form. In word form, that is 97.65 trillion. There. The Sahara Desert covers 97.65 trillion square feet.