#### Answer

$\frac{4}{7}$

#### Work Step by Step

1. Write numerator and denominator as product of primes:
$\frac{20}{35}$ = $\frac{2 * 2 * 5}{5 * 7}$
2. Separate common factors out by writing as a fraction equal to 1:
$\frac{2 * 2}{7}$ * $\frac{5}{5}$ = $\frac{2 * 2}{7}$ = $\frac{4}{7}$