Sue has 100dimes and quarters. If the total value of the coins is $21.40, how many of each kind of coin does she have.

84 quarters and 4 dimes

 300 ft.²   .

Explanation:

We need to find the area of the rectangle:

Area:  A = L * w = length * width = 12 ft. * 18 ft. = 216 ft.²

Then we need to find the area of the TRAPEZOID that is on top of the rectangle:

Area:  A = (1/2) * (base 1 + base 2) * height 
 
             = (1/2) * (18 ft. + 10 ft.) * 6 ft.
   
             = (1/2) * ( 28 ft.) * (6ft.)
      
             =   84 ft.²

Now, we add the 2 (TWO) areas together, to get the

   216 ft.²  +  84 ft.²  = 300 ft.²  .