those are mixed fractions, so first you have to make them improper fractions, multiply the whole times the denominator and add the numerator, that will be you new numerator, then copy your denomminator.
81/8 + (29/8 + 23/8) Since they already have the same denominator use order of operations to proceed, 81/8+57/8 = 138/8 =17 2/8 = 17 1/4