Abigail is putting tiles on a table top. she needs 48 tiles for each of 8 rows. each row will have 6 white tiles.
the rest of the tiles will be purple. how many purple tiles will she need?

I think its like this 
each row has 6 white tiles
8 rows = 48 tiles 
48 - 6 = 42
42 x 8 = 336
so 8 rows = 6 white tiles and 42 purple tiles to make 48 tiles so she will need 336 more tiles to make each 8 rows have 48 tiles

hope this helps : )