Yoga can help improve your ability to concentrate.
In a yoga class, not only do you have to listen to lots of different instuctions relating to the pose, you have to be able to direct those instructions to varying parts of your own body. This takes a lot of concentration as you 'tune' yourself in to what is happening as you work or relax different areas of the body. Yoga is of course all about bringing together the mind and body.
Another aspect of yoga is balance. Whether it's standing on one leg or doing a handstand, in order to balance, you have to concentrate.
All this concentration can help to bring about calmness to the stresses of daily life. Once you begin a regular yoga practice, you should find your ability to focus on things improves, whether it's with tasks at work, or running a 10k!