Well the best answer for LCD is

is 5(x+3y) and the best answer for LCD is

is 2(x+3y)
I hope this helps!
The problem here takes a brilliant mind to answer this. This problem can easily be answered using programming because we can not then and there push all the possibilities using paper and pen.
The answer is 3816547290.
Trying all the possibilities starting form 1000000080 (we are sure that the last number should be 0). Then traversing that number until 9999999990. Each traverse, check the number if its divisible to n, so on and so forth.
Answer:
x = -1 y = - 13/6
Step-by-step explanation:
Set 4 is the correct answer because if you multiply 10 by 10 + 20 times 20, you will get 400 and when you multiply 30 by 30 you also get 400 which is equal to 400 there for you answer would be set 4.
Hope I helped if I did click the thx button ;)