This all deals with order of operations which is: PEMDAS. Parentheses, Exponents, Multiply/Divide, Add/Subtract. The '/' means that you just do whichever one shows first from left to right. So...

12/5*9/8. From left to right you have a division first.

1) 12/5

Next multiply 12/5 times 9

2) 12/5 * 9 = 108/5

And divide 108/5 by 8. You can reduce this statement from 108/5/8 = 108/5 * 1/8 = 108/40 = 27/10 = 2.7

In the problem of your title I saw you also have 3/5 divided by 3/4. That is just...3/5/ / 3/4 = 3/5 * 4/3 = 4/5

Did that help? If so can you best my answer please? (Choose my answer as the best answer)