## Elementary Technical Mathematics

$$\frac{ 43 }{9 \ x y^2}.$$
We divide by the monomial as follows: $$\frac{215x^2y^3}{45x^3y^5}=\frac{5\cdot 43 }{5\cdot 9 \ x y^2}=\frac{ 43 }{9 \ x y^2}.$$ Note that we can not simplify any further, because "$9$" does not go into "$43$" evenly.