1) 3 1/8 + 2 5/6
First, convert the mixed fractions to improper fractions:
3 1/8 = 25/8
2 5/6 = 17/6

Now add the two fractions together:
25/8 + 17/6 = (256)/(86) + (178)/(68) = 150/48 + 136/48 = 286/48

Now, convert the improper fraction back to a mixed number:
286 ÷ 48 = 5 with a remainder of 26, so the answer is 5 26/48

2) 5 11/12 - 3 7/18
First, convert the mixed fractions to improper fractions:
5 11/12 = 71/12
3 7/18 = 59/18

Now subtract the second fraction from the first:
71/12 - 59/18 = (713)/(123) - (592)/(182) = 213/36 - 118/36 = 95/36

Now, convert the improper fraction back to a mixed number:
95 ÷ 36 = 2 with a remainder of 23, so the answer is 2 23/36