Directions: Simplify the following monomials (if possible). 12.) 12b + 8a - 10b
13.) 13y² + 9y + 4y² - 31y
14.) 10m²n + 7mn² - m²n
15.) Find the sum of 16y² and -5y²
16.) Find the difference of 10x²y and 2x²y

-ANYONE PLEASE HELP ME I REALLY NEED THE ANSWER RIGHT NOW BECAUSE I HAVE TO PASS THIS LATER AND THE DEADLINE IS TODAY I HOPE Y'ALL CAN HELP ME:(
I'LL MARK YOU AS THE BRAINLIEST!​

Find the value of x. round the length to the nearest tenth

What are two numbers that have a sum of 15?

Which account has the highest effective annual interest rate? not necessary but show how you got your answer.a. account 1: interest is compounded quarterly at an annual rate of 4.20%.b. account 2: interest is compounded monthly at an annual rate of 4.15%.c. account 3: interest is compounded semiannually at an annual rate of 4.10%d. account 4: interest is compounded annually at a rate of 4.25%.