18. the sahara desert is the largest desert in the world. it covers 3,500,000 square miles. the australian desert is the second largest desert. it covers 2,030,000 square miles less than the sahara. how big is the australian desert?

Solution:
3,500,000 - 2,030,000 = 1,470,000 square miles
Explanation:
Let's fully understand what this word problem is saying. Break it down.
The Sahara Desert is the largest desert in the world.
The Australian Desert is the second largest desert. 
This means that the Australian Desert has an area that is less than the Sahara desert. 
We are given the size of the Sahara, which is 3,500,000 square miles, but not the size of the Australian desert.The area of the Australian desert is less by 2,030,000 square miles.This is the amount we have to subtract from the area of the Sahara to find the size of the Australian desert:
3,500,000-2,030,000= 1,470,000 square miles. Hope this helps!