They want you solve this equation


    2*2800 = ,


where t is the time (in years).


It is direct translation of the text formulation to Math.


To solve this equation and find "t", first divide both sides by  2800. You will get


    2 = .


Take the natural logarithm of both sides. You will get


    ln(2) = 0.037*t,


    t =  = 18.73.


ANSWER.  18.73 years are needed.  It is about 18 years and 9 months.


         19 years is enough.