First, we need to find 1/4 of 2000 in order to find how many blocks he gave away. To do this, we need to do 1/4*2000 to get 2000/4. This can be simplified to 500 by dividing the numerator and denominator by 4.
Then, we can do 2000-500 to find that he must have had 1500 blocks left.
2000 blocks divided into 4 smaller sections of blocks will give you 500 blocks to each section. Therefore 2000-500=1500. Brian keeps 1500 blocks and gives Tia 500 blocks.