Respuesta :

d= (LR_2)/(R_2+R_1) 
d(R_2+R_1)= LR_2 
d(R_2+R_1)/(R_2)= L 
L= d(R_2+R_1)/(R_2) 

The answer I obtained is the same answer as the third choice. 

L= d(R_2+R_1)/(R_2) 
L= (R_2+R_1)d/(R_2) 
L= (R_2+R_1)(d)/(R_2) 
L= ((R_2+R_1)(d))/(R_2)