1. Problem: Given positive integers $a, b, c, d$ satisfy the equation $$a + \frac{1}{b + \frac{1}{c + \frac{1}{d}}} = \frac{23}{16}.$$ Find the value of $a + b + c + d$.
2. First, note that $a, b, c, d$ are positive integers and the expression is a continued fraction.
3. Since $a$ is an integer and the whole expression equals $\frac{23}{16} = 1 + \frac{7}{16}$, we try $a=1$ because $1 < \frac{23}{16} < 2$.
4. Substitute $a=1$:
$$1 + \frac{1}{b + \frac{1}{c + \frac{1}{d}}} = \frac{23}{16} \implies \frac{1}{b + \frac{1}{c + \frac{1}{d}}} = \frac{23}{16} - 1 = \frac{7}{16}.$$
5. Invert both sides:
$$b + \frac{1}{c + \frac{1}{d}} = \frac{16}{7} = 2 + \frac{2}{7}.$$
Since $b$ is a positive integer, try $b=2$.
6. Substitute $b=2$:
$$2 + \frac{1}{c + \frac{1}{d}} = \frac{16}{7} \implies \frac{1}{c + \frac{1}{d}} = \frac{16}{7} - 2 = \frac{16}{7} - \frac{14}{7} = \frac{2}{7}.$$
7. Invert again:
$$c + \frac{1}{d} = \frac{7}{2} = 3 + \frac{1}{2}.$$
Since $c$ is a positive integer, try $c=3$.
8. Substitute $c=3$:
$$3 + \frac{1}{d} = \frac{7}{2} \implies \frac{1}{d} = \frac{7}{2} - 3 = \frac{7}{2} - \frac{6}{2} = \frac{1}{2}.$$
9. Therefore, $d=2$.
10. Finally, sum all values:
$$a + b + c + d = 1 + 2 + 3 + 2 = 8.$$
Answer: 8 (Option D).
Continued Fraction D568D5
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