​+(x+21)(x+34)13​=(x+3)(x+34)x​

\(\frac{1}{x + 3} - \frac{1}{x + 10} + \frac{1}{x + 10} - \frac{1}{x + 21} + \frac{1}{x + 21} - \frac{1}{x + 34} = \frac{x}{\left(\right. x + 3 \left.\right) \left(\right. x + 34 \left.\right)}\)

\(\frac{1}{x + 3} - \frac{1}{x + 34} = \frac{x}{\left(\right. x + 3 \left.\right) \left(\right. x + 34 \left.\right)}\)

\(\frac{\left(\right. x + 34 \left.\right) - \left(\right. x + 3 \left.\right)}{\left(\right. x + 3 \left.\right) \left(\right. x + 34 \left.\right)} = \frac{x}{\left(\right. x + 3 \left.\right) \left(\right. x + 34 \left.\right)}\)

\(\frac{31}{\left(\right. x + 3 \left.\right) \left(\right. x + 34 \left.\right)} = \frac{x}{\left(\right. x + 3 \left.\right) \left(\right. x + 34 \left.\right)}\)

\(\Rightarrow x = 31\)