I have seen questions like this beore so here are a coupple hints and steps!!!
1. Start by labeling your diagram with the information already known.
2. After that can you use similar triangles and ratios of the different numbers?? Just a thought
I dont really know what they mean science but try those 2 hints and see if you can figure out an explnation just explaning those steps!
If you need more help please ask agian.