well you would figure out a common denominator for all fractions.
3 1/8
4 1/2
5 1/4
the common denominator would be 8. so multiply all the fractions by the number that would give you 8 on the bottom of the fraction
1/8 x 1 = 1/8
1/2 x 4 = 4/8
1/4 x 2 = 2/8
now you would set up your problem
3 1/8 + 4 4/8 + 5 2/8
first add the fractions
1/8 + 4/8 + 2/8 = 7/8
then add the whole numbers
3 + 4 + 5 = 12
now put the number and fractions together and you have your answer
12 and 7/8
