(2) 算出R1再和3欧姆串联后的总电阻值:R1+ 3; (3) 计算电流: I= 12/(R1 + 3); (4) 流过8欧姆电阻的电流为: I * 10/(10 + 9 + 8)= 120/[27(R1+ 3)]