Given that Dennis
makes a tile table. He uses 2 boxes of 1,000 red tiles, some boxes of
100 blue tiles an 8 boxes of 10 green tiles. He uses 3,380 tiles in all.
Let the number of boxes of 100 blue tiles be x, then
2(1,000) + x(100) + 8(10) = 3,380
2,000 + 100x + 80 = 3,380
2,080 + 100x = 3,380
100x = 3,380 - 2,080 = 1,300
x = 1,300 / 100 = 13.
Therefore, the number of boxes of blue tiles Dennis used is 13.