I am asked to find $Var(W_t^3- \int_0^t3W_sds)$. This is what I have done so far:
$VarY_t=\mathbb{E}(Y_t)^2=\mathbb{E}(W_t^6-2W_t^3\int_0^t3W_sds+(\int_0^t3W_sds)^2)$
I calculated by applying Ito formula twice on $W_t^6$ that $\mathbb{E}(W_t^6)=15t^3$
but I do not know how to calculate the expectation of the last two terms.