The cellular connection buys new model Z-phones for $80 each and sells them for $200. What is the percent markup, n, for the model z-phone?

The jewelry store is having a sale. necklaces that were regularly priced at $23.50 are on sale for $18.80. what is the percentage of decrease in the price of necklaces?

Ascientist wants to use a model to present the results of his detailed scientific investigation. why would a model be useful? a )because the model makes the concepts easier to understand b) because the model is easy to put together and to use c) because the model prevents other scientists from asking questions d) because the model requires the audience to pay full attention to it i don't know what to choose because between a and d a is much more likely than d because it only wants to get the attention of the audience. i'm confuse.

Whats are the trickiest steps to do when adding or subtracting rational expressions? how does knowledge of rational numbers u in adding and subtracting rational expressions?