I'm sorry I would help but I'm going to have to say b sorry for not being able to show
7a + 6c + 9a - 15c
-- Look for all the 'a's 7a, 9a
-- Addum up 16a
-- Look for all the 'c's 6c, -15c
-- Addum up -9c
-- Write the results 16a - 9c
Answer:
6. x=4
7. x=9
8. x= 13
Step-by-step explanation: