Question 1: Like terms have the same variable, so it is 7b and b.
Question 2: Should be 6y and -9y..
Question 3: the answer is 1. It's 2n because it has the same variable.
Question 4:3a2b
Question 5: 2
Question 6:4x
Question 7:11v
Question 8:-8n
Question 9:-2x
Question 10:-2x this is the same as question 9?
Question 11:2r-14
Question 12:7m-7