(X-2)(X+9)-(5X)= area.
The equation (X-2)(X+9) represents the area of the entire rectangle including the clear and shaded region. That would be X^2+6X-18. Then find the area of the white/clear area, 5X, and subtract that from the equation.
That would make the answer X^2+X-18.
(P.S ^2 refers to the exponent 2)