Answer
$\frac{2}{b^{10}}$
Work Step by Step
Group factors with the same base: $$\frac{20b^{10}}{10b^{20}}$$
$$=(\frac{20}{10})(\frac{b^{10}}{b^{20}})$$
When dividing factors with the same non-zero base, subtract the exponent of the denominator from the exponent of the numerator:
$$=2b^{(10-20)}$$
$$=2b^{(-10)}$$
Write as a fraction and move the base with the negative exponent to the other side of the fraction and make the exponent positive:
$$=\frac{2}{b^{10}}$$
