use only positive exponents and all variables are real positive numbers
y^9/8 / y^5/8
=9/5 (is this right?)
No it isn't right. When you divide one power of y by another power of y, you can just subtract the exponents. Thus the answer is y^(9/8 - 5/8) = y^4/8
= y^1/2 (which is the square root of y)