In the floor of a particular kitchen owned by an abstract artist, each row of tiles to the right of the first row contains two fewer tiles than the row directly to its left. If there are nine rows in all and a total of 504 tiles in the floor, how many tiles does the leftmost row contain?

Classic arithmetic sequence disguised as a tile problem. Once I realized each row drops by 2, I just set up the sum formula and it fell out pretty quickly. Solid 600-level question.

Wait, I need to read carefully — the row to the RIGHT has fewer tiles than the row to its left. So the leftmost row is the biggest one. Almost set it up backwards, that would've cost me.

I just plugged in the answer choices starting from the middle. Since it's only 9 rows and a fixed total, working backwards from the total is way faster than algebra for me.

Nine rows, decreasing by 2 each time — that's symmetric around the middle row. The middle (5th) row is basically the average of all the rows, so total ÷ 9 gives you the middle row directly, then just add back the steps to reach the leftmost. Nice little shortcut.