It's a refrigerator magnet that was for sale by Forever 21, a store aimed at young women. While the item is now listed as "Out of stock", hopefully pulled due to bad publicity, it's available as a t-shirt on Amazon as well.
This really pisses me off. Not only as the father of a beautiful 10 year old girl who does very well in math, but at how damaging and insulting this message is to young women.
If you purchase something like this, you're not too pretty to do math, you're too fucking stupid.