make them both improper fractions (bigger number on top)
7 * 10 + 7 = 77, so 7 7/10 = 77/10
2 * 12 + 6 = 30, so 2 6/12 = 30/12
now we have 77/10 + 30/12
we can reduce the 30/12 by dividing the top and bottom by 2
now we have 77/10 + 15/6
we can't add the tops together because the bottoms are different.
the smallest number that both 10 and 6 go into is 30. 30 is the "least common multiple" of 10 and 6.
multiply the top and bottom of 77/10 by 3: 231/30
multiply the top and bottom of 15/6 by 5: 75/30
now we have 231/30 + 75/30
the bottoms are the same, so we can add the tops like this:
(231+75)/30
306/30
turn it back into a mixed fraction
10 6/30
reduce
10 1/5