Can't get wifi in the other room

[cHk4]

It's really annoying but I can't seem to get wifi in half of the rooms in my house. Is there anything I can buy to make it so devices in other rooms can connect?

Thanks

 

[cHk4]

I wouldn't say it was big, maybe where the wifi is needed it about 10 meters away and there are a few walls but not too big.

Thanks for pointing me in the right direction though I'll take a look Any recommendations on brand/model? I had a look at the Powerline Wireless adapters, how exactly do they work? Do I need 2?