Charlie should order 22 boxes of floor tiles.

**Step 1**

Draw a diagram of the space.

**Step 2**

Find the area of the space. Separate the space into a triangle and a rectangle.

- Find the area of ABCE.

Use the formula A = lw.

A = 20 ft x 8 ft

Area of rectangle ABCE = 160 ft^{2}

- Find the area of the triangle AED.

se the formula A = bh.

A = 1/2 20 x 8

Area of triangle AED = 80 ft^{2}

- Add the areas of ABCE and AED.

160 ft^{2} + 80 ft^{2}= 240 ft^{2}

**Step 3 **

Find how many tiles are needed.
- 1 tile = 1 square foot
This means that for each square foot of floor space, Charlie needs 1 tile.
For 240 ft
^{2} of floor space, Charlie will need 240 tiles.
- Add 2 dozen extra tiles for replacements.
240 tiles + 24 tiles = 264 tiles
- The tiles come in boxes of a dozen.
- Divide.
264 tiles ÷ 12 = 22 boxes of tiles