Answer
$\frac{m-k}{km}$
Work Step by Step
$k^{-1}-m^{-1}$
1. Use exponent rules (any expression raised to the power of -1 equals its reciprocal):
$\frac{1}{k}-\frac{1}{m}$
2. Find a common denominator (in this case it is km):
$\frac{1\times m}{k\times m}-\frac{1\times k}{m\times k}$
3. Simplify:
$\frac{m}{km}-\frac{k}{km}$
4. Combine fractions to get your answer:
$\frac{m-k}{km}$
