Mari has 28 wooden cubes she what's to stack them to form a triangle each row will have one block fewer then the row below it how many blocks will be in the bottom row of the pyramid?

This is a problem involving the sum of numbers
one way is to just add them
1 row=1
2 row=3
3 row=6
4 row=10
5 row=15
6 row=21
7 row=28

each row has the number of blocks that is the row
7th row=7 blocks

so 7 blocks