As the variable x represents the number of times the figure is enlarged, to find the length of the image after it has been enlarged 3 times, we just need to use the function f(x) with the value of x = 3:
f(x) = 3 * (1.9)^x
f(3) = 3 * (1.9)^3
f(3) = 3 * 6.859
f(3) = 20.577 inches
Rounding to nearest hundredth, we have f(3) = 20.58 inches
So the length of the image after being enlarged 3 times is 20.58 inches