1. ## Double Summation

i am having some trouble with the following question if someone could help me out it would be greatly appreciated!

2 2
E E Xij
i=1 J=1

Sorry if its tough to understand. I just dont get how to do it.

2. First of all replace j with the two values 1 and 2, then replace i with 1 and 2.

$\sum_{i=1}^2\sum_{j=1}^2x_{ij}=\sum_{i=1}^2(x_{i1} +x_{i2})=x_{11}+x_{12}+x_{21}+x_{22}$