To solve the sum $\frac{3}{4} + \frac{5}{6} + \frac{7}{9}$, we need to find a common denominator. The least common multiple (LCM) of the denominators 4, 6, and 9 is 36.

We then convert each fraction to have the common denominator of 36:

$\frac{3}{4} = \frac{3 \times 9}{4 \times 9} = \frac{27}{36}$

$\frac{5}{6} = \frac{5 \times 6}{6 \times 6} = \frac{30}{36}$

$\frac{7}{9} = \frac{7 \times 4}{9 \times 4} = \frac{28}{36}$

Now, we add the fractions:

$\frac{27}{36} + \frac{30}{36} + \frac{28}{36} = \frac{27 + 30 + 28}{36} = \frac{85}{36}$

The final result is $\frac{85}{36}$.

Would you like more details or have any questions?

Here are some related questions you might find useful:

1. How do you find the least common multiple (LCM) of a set of numbers?
2. What are the steps to convert a fraction to have a common denominator?
3. How do you simplify a fraction after addition?
4. What is the process of adding fractions with different denominators?
5. Can you convert improper fractions to mixed numbers?
6. How do you check if a fraction is in its simplest form?
7. What are the properties of fractions that help in addition and subtraction?
8. How do you handle addition of more than three fractions?

Tip: When adding fractions, always look for the least common denominator to simplify calculations.