The given circle has a radius of x and an area of 4, which in turn equals pi*x^2.
Thus, A = pi*x^2 = 4.
Now if we use 3x instead of x for the circle radius, we get A = pi*(3x)^2, or
A = 9pi*x^2, or 9(pi*x^2), which is 9 times as great as te original area (4). Thus, the area of the larger circle is 9(4) = 36 square units.