Question 73975
(y^5)=(y)(y)(y)(y)(y)
(y^5)^3=(yyyyy)^3=(yyyyy)(yyyyy)(yyyyy)=(yyyyyyyyyyyyyyy)=y^15

When and exponent is raised to another exponent just multiply the exponents
{{{((y^5)^3(y^3)^2)/((y^4)^4)}}}
{{{((y^15)(y^6))/(y^16)}}}

When multiplying numbers with the same base and different exponents add the exponents
(y^15)(y^6)=(yyyyyyyyyyyyyyy)(yyyyyy)=(yyyyyyyyyyyyyyyyyyyyy)=y^21

Back to your problem...
{{{((y^15)(y^6))/(y^16)}}}
{{{(y^21)/(y^16)}}}

When dividing numbers with the same base and different exponents subtract the exponents.  Remember which one you start with.
{{{(y^21)/(y^16)}}}= {{{(yyyyyyyyyyyyyyyyyyyyy)/(yyyyyyyyyyyyyyyy)}}}={{{y^5}}}

Be careful because if the smaller exponent is on top your answer would be a fraction...
For example
(x^3)/(x^5)=1/(x^2)