What does the news item say about Salman Khan?

Salman Khan’s disembodied voice is heard every day—by tens of thousands of students around the world who are hungry for help learning math. He has posted 1, 200 lessons on YouTube... lessons that appear on an electronic blackboard, and range from basic addition and advanced calculus to science and finance. And they are free.
    Salman Khan lives in California’ s Silicon Valley, with his wife, a rheumatologist in training at Stanford University, and their new baby. He got the idea for Khan Academy four years ago, when he taught a young cousin how to convert kilograms to grams. With Khan’s help, the cousin got good at math, and Khan launched a new career.
    Now, Khan records his lessons from a converted closet in the back of his bedroom. He never goes on camera.
    When the all-girl Castilleja School in Palo Alto, California invited Khan to speak in person— he immediately connected to the students there.
    The concept of short lessons that can be played over and over again attracted high school senior Bridget Meaney. She says she had trouble with seventh grade algebra.
    Originally, Khan kept his lessons short because of YouTube restrictions. Now, he thinks short is better.
    For Khan, teaching math, science, and finance is just the beginning. He says he’s ready to expand his YouTube site to include other subjects as well.