ANSWER
The length of a side is
![12 \: units](https://img.qammunity.org/2019/formulas/mathematics/middle-school/gd8hnmr984kss9wdwkvqt8ilp9wd4fbhhb.png)
EXPLANATION
The rhombus has all sides equal just like the square.
So
![|JK|=|JM|](https://img.qammunity.org/2019/formulas/mathematics/high-school/gs1bi5nrjldkyaxunxj9xz11m80kfjb8wk.png)
We can therefore write the following equation and use it to find x.
![3x = 2x + 4](https://img.qammunity.org/2019/formulas/mathematics/high-school/lba1j56mktq2309wogjjl939ver9jimw8p.png)
We group like terms to get,
![3x - 2x = 4](https://img.qammunity.org/2019/formulas/mathematics/high-school/wxl6zpslvnidgko68lptobvd8z4rx2fecf.png)
This implies that,
![x = 4](https://img.qammunity.org/2019/formulas/mathematics/high-school/atvjgwdx0v4qkei0dce4beeina444xt06p.png)
We substitute the value of x in to the expression for one side to get,
![JM=3 * 4 = 12 \: \: units](https://img.qammunity.org/2019/formulas/mathematics/high-school/k3k9i8tv4qv5uebibrou1rvhbfxeyv6alk.png)