(* 10. tyden
20*Log10[(Uout/Uin)]
*)

(* 1 *)
Solve[20*Log10[x]==12]//N

(* 2 *)
Solve[20*Log10[(1/x)]==-18]//N

(* 3 *)
res1=Solve[20*Log10[(5/10)]==x-5-3]//N

res2=Solve[20*Log10[(x/10)]==-5]//N (* napeti *)

Solve[20*Log10[(5/x)]==-3]//N

Solve[20*Log10[(x/((x/.res2)))]==(x/.res1)]//N (* kontrola *)

(* 4 P = U * I *)
(* 5 *)
230*16≥3600

(* 6 | U=(Um/(Sqrt[2]))*)
ue=220;
p=1850;
i=(P/Ue)//N  (* a *)

r=(ue/i)//N (* b *)

(* c *)
um=ue*(Sqrt[2])//N
im=i*(Sqrt[2//N])

(* d *)
i2=(240/r)//N
p2=240*i2//N

(* 7 asi *)
ClearAll["Global`*"]
p=600;
u=230;
i=(p/u);
r=(u/i)//N
i//N
pmin="W"220*i//N
pmax=240*i//N
uamin=220*(Sqrt[2])//N
uamax=240*(Sqrt[2])//N

(* 8 asi *)
ClearAll["Global`*"]
p=3500;
u=230;
i=(p/u)//N

(* 9 asi *)
ClearAll["Global`*"]