помогите! !!!!
(3,1d-d):0,2=1,05

(3,1d-d):0,2=1,05
(3,1d-d)=1,05*0,2
(3,1d-d)=0,21
d(3,1-1)=0,21
2.1d=0.21
d=0.21:2.1
d=0.1
Проверим:
(3,1*0.1-0.1):0.2=1.05
0,21:02=1.05