Let N be the number...so we have
N^(1/2) = 2N^3 rearrange as
2N^3 - N^(1/2) = 0 factor
N^(1/2) (2N^(2.5) - 1) = 0 set each factor to 0
N^(1/2) = 0 → N = 0 [ reject.....0 isn't positive...]
And
2N^(2.5) - 1 = 0 rearrange
2 N^(2.5) = 1 divide by 2
N^(2.5) = 1/2 → N = (1/2)^(1/2.5) = (.5)^(0.4) ≈ .75786