>>807
 AR = (1/(1+t))AC,
 BG = (x/(x+3))BR,
∴ 僊BG = (1/(1+t))(x/(x+3))僊BC,
題意より
 (1/(1+t))(x/(x+3)) = 1/8,
∴ t = 43/13, x = 7/2.