Adding random variables

#1
Hello, i need some help with an assignment.

we have two random variables x1 and x2. E[x1]=E[X2]=1, VAR[X1]=4 and VAR[X2]=5.

Y=1/3(3X1-6X2)

Find VAR[Y],

I think I have to just do this:
1/3(3*VAR[X1]+6*VAR[X2]) and get: 1/3(3*4+6*5)=14

Can anyone confirm or explain my mistake if it's wrong, thank you so much!