Hi, TRUEBOSS72!
The answer to your question I believe is

-ASIAX ∵<span>Frequent Answerer</span>∴
P.S. If I am wrong about it please let me know.
4 x 4 = 16
5 x 5 = 25
6 x 6 = 36
If we made it into a ratio of residential customers to business customers, it would be a 2:1
350/2 = 175
350 + 175 = 525
525 total customers
Sorry for not giving you the calculation here -
5/12 and 2/9 have denominators divisible by only 3 right? Well The common denominator that can then change is 3 because that's the only number they have in common (except 1)