please help me on #2 only. please tell the process

We are given a rhombus and we are asked to find the length of one of its diagonals. To do that let's remember the following relationship:
[tex]AE=EC[/tex]Therefore, we have:
[tex]AC=2AE[/tex]Replacing the known values:
[tex]AC=2(8)=16[/tex]Therefore, AC is 16