I can tell you what is says in english and then answer it!
1. You ___ the black pants by the white pants
The full sentence looks like this in spanish depending on the filler you use i personally picked 3 (three) good ones for you!
1. buy
2.have
3.love
im going with buy! so it looks like this in english first
4. $ you buy the black and white pants
5. in spanish though its $ compras los pantalones blancos y negros.