Problem #$1$: VECTORS in $3$D

Let vec$(u)=($:$2,4,-5$:$)$ and vec$(v)=($:$-6,10,2$:$).$

A$)$ Compute: vec$(u)-3$vec$(v).$

B$)$ Compute: $|vec(u)+$vec$(v)|.$

C$)$ Find the unit vector with the same direction as vec$(u).$

D$)$ Find a vector parallel to vec$(v)$ with length $20.$

E$)$ Computer vec$(u)*vec(v)$ and the angle between vec$(u)$ and vec$(v).$