first, convert everything to improper fractions (bigger numbers on top)
6 * 3 + 1 = 19, so 6 1/3 = 19/3
4 * 4 + 3 = 19, so 4 3/4 = 19/4
3 * 12 + 7 = 43, so 3 7/12 = 43/12
so now you have
19/3 + 19/4 + 43/12
the bottoms (denominators) are different, so you can't add the tops (numerators) together.
we want to make the bottoms all the same. 3 goes into 12. 4 also goes into 12.
we want to make the bottoms all 12. 12 is the "least common multiple" of 3, 4, and 12
for the 19/3, multiply the top and bottom by 4
19/3 = 76/12
for the 19/4, multiply the top and bottom by 3
19/4 = 57/12
now we have 76/12 + 57/12 +43/12
the bottoms are all the same, so we can combine the tops like this:
(76+57+43)/12
176/12
reduce. divide the top and bottom by 4
44/3
14 2/3