Translation:Andi went to the bookstore without pants.
Meaning: Andi went to the bookstore without a pants.
"... without a pants" , that's not correct I think.
I think that you can't use the article "a"with "pants".
"pants" is a plural noun.
It should be "without pants".
Although I honestly think that it's better to visit a bookstore wearing pants.
But, that's just me.