7. (10 points) A string of beads consists of 31 beads, with the most expensive one in the exact middle. Starting from one end, each subsequent bead is 3 yuan more expensive than the previous one, up to the middle bead. Starting from the other end, each subsequent bead is 4 yuan more expensive than the previous one, up to the middle bead. The total value of the string of beads is 2012 yuan. What is the value of the middle bead? $\qquad$ yuan.
【Solution】Solution: According to the analysis, assume the value of the middle bead is $a$. By the property of an arithmetic sequence, the total value of the first 15 beads is: $(a-3 \times 8) \times 15$ yuan, and the total value of the last 15 beads is: $(a-4 \times 8) \times$ 15 yuan,
$$
\therefore(a-3 \times 8) \times 15+(a-4 \times 8) \times 15+a=2012 \text {, }
$$

Solving this, we get: $a=92$,
The value of the middle bead is 92 yuan.
Therefore, the answer is: 92 .