Answer:
2 millimeters
Step-by-step explanation:
1. Set up the equation
(5 · 12) + (5 · 12) + (12 · d) + (12 · d) + (5 · d) + (5 · d) = 188
2. Simplify
60 + 60 + 12d + 12d + 5d + 5d = 188
120 + 34d = 188
3. Solve
34d = 68
d = 2
