Answer:
2/3
Explanation:
Look at what you are getting on the right hand question. 10a +10b has a common factor that can be pulled out. It is 10
10a + 10b = 10(a + b)
Now look at the denominator
9x - 9y = 9(x -y)
There are a lot of possible answers.
Mine would be to multiply 3/5 * 10/9

so
(10a + 10b)/(9x - 9y) = 2/3