The universal set, U, is the numbers from 12 to 40 ( including 12 and 40 ), set A is the multiples of 4 in U, and set D is the multiples of 8 in U
for A, all numbers that divide evenly by 4 from your set, so
A = { 12, 16, 20, ... , 40 }
D = ( 16, 24, .... , 40} <---- all numbers that evenly divide by 8