Question

what is the least common denominator of 1/12 and 3/8

Answer 1

that is finding the least common multiplier of 12 and 8, and that is 24:
1/12 = 2/24
3/8 = 9/24

Answer 2

for 1  1/12
LCM: 1, 2,3,4, 6, 12
for 3/8
LCM: 1, 2, 4, 8
Both have 4 in common