In one year, a school uses 13,280 pieces of white paper, 5,580 fewer pieces of blue paper than white paper, and 3,400 fewer pieces of yellow paper than blue paper. How many pieces of paper does the school use in all?

The school uses 25,280 pieces of paper in total.

Explanation:

To determine the pieces of paper that the school uses in total, the following equation must be performed:

White: 13,280

Blue: 13,280 - 5,580

Yellow: 13,280 - 5,580 - 3,400

White + Blue + Yellow = X

13,280 + 13,280 - 5,580 + 13,280 - 5,580 - 3,400 = X

(13,280 x 3) - (5,580 x 2) - 3,400 = X

39,840 - 11,160 - 3,400 = X

25,280 = X

Therefore, the school uses 25,280 pieces of paper in total.

the present continuous is a verb tense which is mainly used to indicates that an action is in progress at the moment of speaking.  

it is formed using: person + verb to be (am/is/are) +verb + - ing form  

example: i am studying at this moment .

in addition, the present continuous is also used in order to express things that will or will not happen in the near future.

example: i am having dinner with some friends tonight.

the speaker sometimes   uses it   to express that an action is repeated and it causes irritation on the part of the speaker

example: my sister is constantly complaining about everything.

lets none because you provide no details.