Hello Guys !! In This photos i found that in (a) : RT= 4 Ω+ 10 Ω+ 4 Ω= 18 Ω and in (d) : RT= 10 Ω but i can't understand why in (a) the total resistance equals to 18 and how will the current would pass ?? and in (d) i can't understand why the total resistance equals to 10 and why we didn't take the two 4 ohm resistances in the count ?!! Thank you Guys !!