Please, use ( ) around fractional coefficients:
1/3x-9y, 6/5x-15y should (probably) be written as (1/3) - 9y and (6/5)x - 15 y.
The LCD here is 3(5) = 15.
Mult. 1/3x-9y and 6/5x-15y by 15, and then divide the result by 15:
15 [ (1/3)x - 9y and (6/5)x - 15 y ]
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15
This simplifies to:
5x - 135y and 18x - 225y
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15 15
These fractions are equivalent to the original ones, but now the common denominator, 15, is evident.
