$1)$ What is the total variance of the following portfolio including $2$ assets invested in the

ratio of $1$:$2.A$:$E(r)=0\mathrm{.}2,=0\mathrm{.}5E(r)=0\mathrm{.}4,=0\mathrm{.}7rf=0\mathrm{.}1Q2$

I need help with the second question in the picture Please explain in a easy and understandable way

the first one answer is B $=0\mathrm{.}12$