Question

(у+1,05)*20,1=209,04

Answer 1

y+1.05= 209.04:20.1=10.4
y= 10.4-1.05= 9.35

Answer 2

(y+1,05)*20,1=209,04
y+1,05=209,04:20,1
y+1,05=10,4
y=10,4-1,05
y=9,35
Проверка
(9,35+1,05)*20,1=209,04
1)9,35+1,05=10,4
2)10,4*20,1=209,04