12.
Add like terms from both trinomials:



Combine these terms to get a new trinomial as your answer:

13.
Subtract like terms from both trinomials (note that subtracting a negative is the same as adding it as a positive):



0 can be left out of the answer.
Combine these terms to get a binomial as your answer:
Answer:22
Step-by-step explanation:
We want to solve the equation :

first, multiply both sides by 4:


divide both sides by 3:

add -3 to both sides:

Answer: x=9