What is the area of the polygons by composition

The rectangle has the dimensions 4 x 3. 
The measure of 6 ft is the triangle plus the square's length. 
The rectangle's length is 3. 
To find the triangle's width, solve this: 3 + x = 6 
Subtract 3 from each side to get x = 3. 
The dimensions of the triangle is 3 x 4. 
The area will be half of 3 x 4, so 12 / 2 or 6. 
The rectangle's area is 12 because its dimensions are 3 x 4. 
12 + 6 = 18 feet total. 

Hope this helps!