What is the sat writing and language test asked students to do

How do you work out 21.3-8= show your working. plz

28. the new systematic nomenclature was so ( that many chemists preferred to ( the older trivial names that were at least shorter. at least, that is the ostensible reason. actually, tradition seems to carry more weight than ( with some scientists.

Spider crabs live in the shallow regions of the ocean floor. algae tend to grow on the surface of spider crabs. the algae provide the crabs protection from predators by camouflaging them. the spider crabs give the algae shelter. what does this description suggest? 1. the algae are parasites of the spider crabs. 2. the algae and the spider crabs have a mutualistic relationship. 3. the spider crabs are commensals, and the algae are parasites. 4. the spider crabs benefit from the algae living on them. 5. the spider crabs are parasites of the algae.