What is 283,980 written in expanded form?

Expanded form of 283,980 is:

200,000 + 80,000 + 3,000 + 900 + 80

Expanded form is adding the numbers according to its place value. 

We based the value of the digit on its place.

2 is in the hundred thousands place. 2 x 100,000 = 200,000
8 is in the ten thousands place.         8 x   10,000 = 80,000
3 is in the thousands place.               3 x     1,000 = 3,000
9 is in the hundreds place.                 9 x       100 = 900
8 is in the tens place.                         8 x          10 = 10