Remember, to solve this, you multiply the bigger numbers and add the exponents. if the exponents are negative they go on the bottom and are switched to a positive, you are trying to make the problem positive.
number 15 is A because you multiply 2 and 4 to get 8 and you add the exponents together if they are positive and are not a fraction
number 16 is D because you multiply all the bigger numbers together to get 48, then you add all the b's together to get four and all the a's to get 8
number 17 is D because you do the same by multiplying 5 and 3 to get 15, then adding the exponents to get 3 x's and 6 y's
number 18 is D because you multiply 5 and 2 and add the exponents to get 3 x's and 5 y's because the x without a number is a one so you make that one count and add 2 and one together to get 3
number 19 is B because the smaller number is negative so the y goes to the bottom and it becomes a y^3
number 20 is A because both exponents are negative and go to the bottom and become positive
number 21 is D because its the same case as number 20
Lastly Number 22 is B
I hope this helps and is correct lol