Big square length is 14 and small square length is 7. what is the area of dark part?

The answer would be 36.75 units squared because the area of the big square is 196 units squared, then take away (minus) the area of the smaller square, 49 units squared is 147 units squared, then simply divide it by four because the grey area represents a fourth of the space in between the squares so that brings you to 36.75 units squared.