Answer this to be marked as brainliest

1. a. before you can subtract these two decimals, what must you do?
(you are not solving, you are telling me what you need to do before you can solve by hand)
10.64 - 8.5

2. a. write an expression that represents how to find the answer to the problem below.

b. then, show all of your work, by hand, to solve your expression.

state your answer in a complete sentence, making sure to answer the question!
you are working as an assistant to an astronomer. the astronomer has asked you to answer the following question.

the star alpha centauri is 4.3 light-years away from earth. the star betelgeuse is about 121 times as far away from earth as alpha centauri. about how many light years away from earth betelgeuse.