The sum is 41/24 in simplest form, or 1 17/24 as a mixed number.
Decimal: \displaystyle 1.708\overline{3} (the 3 repeats forever, about 1.7083)
Percent: 170.83%
1 whole + 17 of 24 equal parts
Step-by-step solution
The problem
\frac{5}{6} + \frac{7}{8}
Write both fractions over 24. List multiples of each denominator until they meet:
Multiples of 6: 6, 12, 18, 24
Multiples of 8: 8, 16, 24
The least common denominator is 24. Multiply the top and bottom of each fraction by the same number, so its value doesn't change.
Check that it can't be simplified. 41 and 24 have no common factor other than 1, so this is the simplest form.
\text{GCF}(41, 24) = 1
Write it as a mixed number. Divide: 24 goes into 41 1 time with 17 left over. The whole number is 1, the remainder 17 becomes the numerator, and the denominator stays 24.