Question 152409
When you divide exponential expressions of the same base, you subtract the exponents.
{{{x^M/x^N=x^(M-N)}}}
In your case x=-11 and M and N are 21 and 19,
{{{(-11)^21/(-11)^19=(-11)^(21-19)}}}
{{{(-11)^21/(-11)^19=(-11)^(2)}}}
{{{(-11)^21/(-11)^19=121}}}