Each exterior angle of a regular decagon has a measure of (3x + 6)°. What is the value of x?

The exterior angles of any polygon add up to 360°. A regular decagon has 10 equal exterior angles, so each measures 360° ÷ 10 = 36°. Set 3x + 6 = 36, then subtract 6 and divide by 3 to get x = 10. The correct choice is B, x = 10.

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