I have intel cpu and i only have one led fan in front side of the case should i install fan on the back side near gpu and cpu?What brand is your CPU? If it's AMD then it's fine (usually) but if it's Intel then you might need to check your fans. But your saying your GPU temperature is high, so you might want to check the case fans to see if they're working.
Yes do that rear fans are very effective than front fans.I have intel cpu and i only have one led fan in front side of the case should i install fan on the back side near gpu and cpu?