2 3/4 + 3,4

To add \(2 \frac{3}{4}\) and \(3.4\), we first need to convert the mixed number into an improper fraction and the decimal into a fraction.

1. Convert \(2 \frac{3}{4}\) into an improper fraction: \[ 2 \frac{3}{4} = \frac{2 \times 4 + 3}{4} = \frac{8 + 3}{4} = \frac{11}{4} \]

2. Convert \(3.4\) to a fraction: \[ 3.4 = \frac{34}{10} = \frac{17}{5} \]

Now we need a common denominator to add the two fractions. The least common multiple of 4 and 5 is 20.

3. Convert \(\frac{11}{4}\) to have a denominator of 20: \[ \frac{11}{4} \times \frac{5}{5} = \frac{55}{20} \]

4. Convert \(\frac{17}{5}\) to have a denominator of 20: \[ \frac{17}{5} \times \frac{4}{4} = \frac{68}{20} \]

5. Now, add the two fractions: \[ \frac{55}{20} + \frac{68}{20} = \frac{55 + 68}{20} = \frac{123}{20} \]

6. Convert \(\frac{123}{20}\) to a mixed number: \[ 123 \div 20 = 6 \quad \text{(remainder 3)} \] So, \(\frac{123}{20} = 6 \frac{3}{20}\).

Thus, the sum of \(2 \frac{3}{4} + 3.4\) is \(6 \frac{3}{20}\).