Ответ:

0.6 Ом

Объяснение:

r23 = R/2 = 1/2 = 0.5 Ом

r456 = R/3 = 1/3 = = 0.3 Ома

r123456 = R1+r23+r456 = 1+0.5+0.3 = 1.8 ом

Rob = R7*r123456 / (R7 + r123456) = 1*1.8 / (1+1.8) == 0.6 Ом