Just plug in the square root of 100 in your calculator (10) and then either leave it as 10/49 or simplify it to a decimal...depending on what your teacher is expecting from you.
I don't remember what is a extraneous solution, but i hope it helps
Try multiplaying all sides
(1/A) dA/dt= C where A is the population of ants and C is a constant
ln(A) = C*t + C1 where C1 is another constant that comes out of integration and t is time in days.
Plugging in: at t=0, A= 100 so C1 = ln(100) = 4.605
at t=3, A=230 so ln(230) = 3*C +4.605 so C = 0.278
Final equation:
ln(A) = 0.278t + 4.605
or:
A = exp(0.278t + 4.605)
After 14 days, A = exp(0.278*14 + 4.605) = 4875.2
