Hi @carlos94587,
The layout you are looking to create can be completed by setting your “flex item” to have flex basis values of 1 0 50%. Then, all the children elements can have an expanded flex basis.
To see the steps I took to complete this layout, feel free to take a look at the following video: https://drive.google.com/file/d/0BynZs0dQwPd_VXJBWHpQLXY2U28/view
Hopefully this helps 