13.) (t⁻⁴)⁻⁹t² Now if the exponents outside of the parenthesis, that means you multiply them. t⁻⁴⁽⁻⁹⁾=t⁴⁵ Next, When it look like this: t⁴⁵ · t², don't multiply! When it comes to this, you had to add the exponents because it has the same base number: t⁴⁵⁺²=t⁴⁷.
Here's your answer to your question, t⁴⁷.