whe can find the area of the total rectangle and then subtract the area of the squares
Rectangle area
the formula is

where b is the base and the height
replacing

The area of the rectabgle is 270 square ft
Squares area
The area of the square is

the area of one square is 9square ft, the are of the both squares is 18square ft
Finally Area
we subtract the area of the squares to area of the rectangle

The total area is 252 square ft