7 = (210+88t)/(2(sqrt(210t+44t^2)))

Is t= 1.0479....?
I got the denominator multiplied by 7 and squared both sides to eliminate the sqrt and then simplified, used the quadratic formula to find the values but since the questions is about squirrels growth it can not be a negative answer, therefore i just calculated one answer, but is it correct?

right. multiply 7 by the denominator, you should get:

7*2sqrt(210t+44t^2) = 210 + 88t
14*sqrt(210t+44t^2) = 210 + 88t
then square both sides:
196(210 + 44t^2) = 7744t^2 + 36960t + 44100
8624t^2 + 41160t = 7744t^2 + 36960t + 44100
880t^2 + 4200t - 44100 = 0
44t^2 + 210t - 2205 = 0
thus, you will get:
t = (21/44)(7*sqrt(5) - 5) , or in decimals,
t = 5.084

*actually there are two roots, but the other is negative so it's extraneous,,

so there,, :)