#### Answer

LCD is 60.

#### Work Step by Step

To find the least common denominator factor each denominator then multiply each factor the greatest number of times it occurs in either number.
$12=\underline2\times\underline2\times\underline3$
$20=2\times2\times\underline5$
$LCD=2\times2\times3\times5=4\times3\times5=12\times5=60$