Answer:
A:(15,18)
Step-by-step explanation:
Hopefully this helps!
9: B right
10: C obtuse
11: B right
12: B right
I hope they are right! Sorry if they are not!
The answer is 19.8 to ur problem
Answer: 
<u>Remove "x" and add</u>
-2 + 9 = 7
<u>Add "x" back</u>
7 -----> 7x
Note: When adding/subtracting problems like these remove "x" and then add/subtract normaly. When you get your answer put x back.
Step-by-step explanation:
Total books = 368.
Sociology books = 92.
Psychology books = 3 times sociology books
= 3 x 92 = 276
Total = 276 + 92 = 368