The way you add 4 digit numbers is by taking each place value and adding them each together. One's get added with ones, tens get added with tens and so on. For example, to add 1864+7528, you would first start off with adding 4 and 8 which gives you 12. The 2 will go under the equation and the 1 will travel to the tens place. Next, 2+6 which is 8 and then add the 1 from 12 which gives you 9. Then, 8+5 which is 13. Again, the 3 will go under the equation and the 1 will travel to the thousands place. Finally, 7+1 which is 8 and then add the 1 from 13 which gives you 9. The sum should be 9392.
