Tower one- 2145046422.09Tower two- 8947346861.26
Both together- 11092393283.4
I believe #7 would be 5:13, #8 to be 6:7, #9 to be 13:18, #10 to be 18:5.
I hope this helps.
It doesn't change because to add fractions, you need a common denominator. To find it, they multiplied 1/3 by 2 to make 2/6, to add to the 3/6.
Least common multiple question
Ronald: count by 6's
6, 12, 18, 24, 30, 36, 42, 48, 54 ....
Tim: count by 9's
9, 18, 27, 36, 45, 54,
every 18 days they do their laundry together