86. Chen Gang and Zhang Qiang started from their respective homes at the same time and walked towards each other. They first met at a point 5 kilometers away from Chen Gang's home. After meeting, they continued to walk at their original speeds. Chen Gang reached Zhang Qiang's home, and Zhang Qiang reached Chen Gang's home, and both immediately returned. As a result, they met again at a point 3 kilometers away from Zhang Qiang's home. Therefore, the distance between Chen Gang's home and Zhang Qiang's home is $\qquad$ kilometers.
Reference answer: 12