the fractions have to have the same bottoms
8 doesn't go into 12, but 8 and 12 both go into 24
24 is the smallest number that both 8 and 12 go into, so 24 is the "least common multiple" of 8 and 12
for 8/12, times by 2 on the top and bottom
8/12 = 16/24
for 4/8, times by 3 on the top and bottom
12/24
8/12 + 4/8 = 16/24 + 12/24
now the fractions have the same bottoms, so you can add the tops
(16+12) / 24
28/24
reduce. divide the top and bottom by 4
7/6 = 1 1/6