So the integral from four to seven of f of x dx, this thing, this thing is equal to two. This thing is depicting that area right over there. So what about this, where we've switched it? Instead of going from four to seven, we're going from seven to four. Well, the key realization is is if you switch the bounds, and this is a key definite integral property, that's going to give you the negative value. So this is going to be equal to the negative of the integral from four to seven of f of x dx. And so this is going to be negative, and we just figured out the integral from four to seven of f of x dx.