ok here we need to make sense of the left hand side

(x/4)^0.5 means the square root of that, so we have (x^0.5)/(4^0.5) which equals (x^0.5)/2, if you do the same on the other one you have (x^0.5)/2^0.5.

sqaure both side to remove the sqaure roots and then you get (x/4) x (x/2) = 2500 ----> x^2 = 20,000 -----> x = 100 x 2^0.5 which approximates to 141