What’s the value for x

We just started the introduction into circles and i have no idea how to do this.

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.

Complete the two-column proof. given: 5/x + 9 = 11 prove: x = 10 5/x + 9-11 select one: a. a. given b. subtraction property of equality c. division property of equality b. a. given b. subtraction property of equality c multiplication property of equality ca. given b. addition property of equality c. multiplication property of d. a. given b. addition property of equality c. division property of equality