Solve the Fraction Equation: Finding the Missing Number in ? + 3/4 = 4/5

To solve this problem, we aim to find $x$ in the equation $x + \frac{3}{4} = \frac{4}{5}$.

Step 1: Isolate $x$ by subtracting $\frac{3}{4}$ from both sides.

$x = \frac{4}{5} - \frac{3}{4}$

Step 2: Find a common denominator for the fractions $\frac{4}{5}$ and $\frac{3}{4}$. The least common denominator of 5 and 4 is 20.

Convert $\frac{4}{5}$ to a fraction with a denominator of 20:

$\frac{4}{5} = \frac{4 \times 4}{5 \times 4} = \frac{16}{20}$

Convert $\frac{3}{4}$ to a fraction with a denominator of 20:

$\frac{3}{4} = \frac{3 \times 5}{4 \times 5} = \frac{15}{20}$

Step 3: Subtract the two fractions:

$x = \frac{16}{20} - \frac{15}{20} = \frac{16 - 15}{20} = \frac{1}{20}$

Therefore, the missing fraction $x$ is $\frac{1}{20}$.