The area of the region enclosed by the parabola $$y = 4x - x^2$$ and $$3y = (x - 4)^2$$ is equal to

Curve 1: $$y = 4x - x^2$$
Curve 2: $$y = \frac{(x-4)^2}{3} = \frac{x^2 - 8x + 16}{3}$$
$$4x - x^2 = \frac{x^2 - 8x + 16}{3}$$, which leads to $$12x - 3x^2 = x^2 - 8x + 16$$, then $$4x^2 - 20x + 16 = 0$$ and $$x^2 - 5x + 4 = 0$$, so $$(x-1)(x-4) = 0$$ and the curves intersect at $$x = 1$$ and $$x = 4$$
Curve 1 lies above Curve 2 on this interval.
The area is calculated as $$A = \int_1^4 \left[(4x - x^2) - \frac{(x-4)^2}{3}\right] dx = \int_1^4 \left[4x - x^2 - \frac{x^2 - 8x + 16}{3}\right] dx =\frac{1}{3}\left[-\frac{4x^3}{3} + 10x^2 - 16x\right]_1^4.$$ 

 $$A  = \frac{54}{9} = 6.$$