Todd has 21 white tiles dnd some black tiles to make a mosaic. the mosaic has a total area of 144 square centimeters. each tile has an area of 3 square. how many black tiles did todd use?

the number of black tiles that Todd used is 27

Step-by-step explanation:

Let x represent the number of black tiles that Todd used.

Todd has 21 white tiles and some black tiles to make a mosaic. Each tile has an area of 3 square. It means that the total area of the white tiles is 21 × 3 = 63 cm^2

The total area of the white tiles is x × 3 = 3x cm^2

The mosaic has a total area of 144 Square centimeters. It means that

3x + 63 = 144

3x = 144 - 63 = 81

x = 81/3 = 27