Coefficient of $x^2$ in $(x+\frac 2x)^6$ I did $6C4 x^2\times (\dfrac 2x)^4$ and got that the coefficient of $x^2$ is $15$, but the answer is $60$, why? Did I miss a step?

You have mistake.
$\binom{6}{4} . x^2 . \left(\frac 2x\right)^4$
= $15 . x^2 . \frac{16}{x^4}$
= $240 . \frac{1}{x^2}$
Here 240 is coefficient of $x^{-2}$ not $x^2$.

Correct term -

$\binom{6}{2} . x^4 . \left(\frac 2x\right)^2$
= $15 . x^4 . \frac{4}{x^2}$
= $60 . x^2$
So answer is 60.
